Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIRST TRUST EXCHANGE-TRADED FUND VIII
Prospectus Date	rr_ProspectusDate	Jan. 02, 2020
First Trust Low Duration Strategic Focus ETF
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Summary Information
Objective [Heading]	rr_ObjectiveHeading	Investment Objectives
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The First Trust Low Duration Strategic Focus ETF (the "Fund") seeks to generate current income, with a secondary objective of preservation of capital.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses of the Fund
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The following table describes the fees and expenses you may pay if you buy and hold shares of the Fund. Investors purchasing and selling shares may be subject to costs (including customary brokerage commissions) charged by their broker, which are not reflected in the table below.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal period January 3, 2019 (inception) through August 31, 2019, the Fund's portfolio turnover rate was 14% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	14.00%
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example, No Redemption Narrative [Text Block]	rr_ExpenseExampleNoRedemptionNarrativeTextBlock	The example below is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. This example does not take into account customary brokerage commissions that you pay when purchasing or selling shares of the Fund in the secondary market. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain at current levels. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal market conditions, the Fund seeks to achieve its investment objectives by investing at least 80% of its net assets (including investment borrowings) in a portfolio of U.S.-listed exchange-traded funds ("ETFs") that principally invest in income-generating securities that provide the Fund with an effective portfolio duration of three years or less. Duration is a measure of the expected price volatility of a debt security as a result of changes in market rates of interest, based on, among other factors, the weighted average timing of the debt security's expected principal and interest payments. In general, duration represents the expected percentage change in the value of a security for an immediate 1% change in interest rates. For example, the price of a security with a three-year duration would be expected to drop by approximately 3% in response to a 1% increase in interest rates. In selecting the ETFs in which the Fund invests, First Trust Advisors L.P., the Fund's investment advisor ("First Trust"), uses a disciplined process for reviewing the macroeconomic outlook, policy drivers and asset level analysis that inform portfolio construction and ongoing risk management. The process begins with a robust, top-down review of macroeconomic factors including monetary and fiscal policies, growth forecasts, trade and tax policies, global market views and current market valuations. The process combines these factors with disciplined bottom-up asset level analysis including views on rates, duration, credit, currency and current asset valuations. First Trust utilizes this process to evaluate the relative attractiveness of the various fixed income asset classes in an attempt to best position the Fund to take advantage of market trends and investment opportunities. Lastly, First Trust seeks to construct a portfolio that provides the target effective duration of three years or less while managing both interest rate risk and credit risk. A significant portion of the ETFs in which the Fund invests may be advised by First Trust. The Fund may invest in ETFs that invest principally in corporate bonds, floating rate loans and fixed-to-floating rate loans, senior loans, mortgage-backed securities, hybrid income securities (including convertible, contingent convertible and preferred securities), government debt and other fixed income securities. The securities to which the Fund may have exposure may be issued by both U.S. and non-U.S. issuers, including both corporate and governmental issuers located in countries considered to be emerging markets. The Fund may also invest up to 40% of its net assets in ETFs that have exposure to U.S. corporate high yield securities (also known as "junk bonds") and senior loans. The Fund may invest up to 20% of its net assets in bonds issued by non-U.S. government and corporate issuers, including up to 10% of its net assets in ETFs holding debt of issuers located in countries considered to be emerging markets. The Fund may also invest up to 10% of its net assets in ETFs holding preferred securities and up to 10% of its net assets in ETFs holding convertible securities. The Fund invests significantly in the First Trust Enhanced Short Maturity ETF ("FTSM"), First Trust Low Duration Opportunities ETF ("LMBS") and First Trust Senior Loan Fund ("FTSL"). See below for a summary of FTSM's, LMBS's and FTSL's principal investment strategies. FTSM FTSM's investment objective is to seek current income, consistent with preservation of capital and daily liquidity. Under normal market conditions, FTSM intends to achieve its investment objective by investing at least 80% of its net assets in a portfolio of U.S. dollar-denominated fixed or floating rate debt securities, including securities issued or guaranteed by the U.S. government or its agencies, instrumentalities or U.S. government-sponsored entities, residential and commercial mortgage-backed securities, asset-backed securities, U.S. corporate bonds, fixed income securities issued by non-U.S. corporations and governments, municipal obligations and other debt securities bearing fixed or floating interest rates. FTSM may also invest in money market securities. FTSM may invest up to 20% of its net assets in privately-issued, non-agency sponsored mortgage- and asset-backed securities. Under normal market conditions, FTSM's portfolio is expected to have an average duration of less than one year and an average maturity of less than three years. Additional information regarding FTSM, including its prospectus and most recent annual report, is available without charge by visiting www.ftportfolios.com/Retail/Etf/EtfFundNews.aspx?Ticker=FTSM. LMBS LMBS's primary investment objective is to generate current income and its secondary investment objective is to provide capital appreciation. Under normal market conditions, LMBS seeks to achieve its investment objectives by investing at least 80% of its net assets in mortgage-related debt securities and other mortgage-related instruments (collectively, "Mortgage-Related Investments"). LMBS normally expects to invest in Mortgage-Related Investments tied to residential and commercial mortgages. Mortgage-Related Investments consist of: (1) residential mortgage-backed securities (RMBS); (2) commercial mortgage-backed securities (CMBS); (3) stripped mortgage-backed securities (SMBS), which are mortgage-backed securities where mortgage payments are divided up between paying the loan's principal and paying the loan's interest; and (4) collateralized mortgage obligations (CMOs) and real estate mortgage investment conduits (REMICs) where they are divided into multiple classes with each class being entitled to a different share of the principal and/or interest payments received from the pool of underlying assets. Mortgage-Related Investments typically represent an interest in a pool of mortgage loans made by banks and other financial institutions. The individual mortgage loans are packaged or "pooled" together for sale to investors. As the underlying mortgage loans are paid off, investors receive principal and interest payments. Mortgage-Related Investments may be fixed-rate or adjustable-rate Mortgage-Related Investments (ARMS). LMBS limits its investments in Mortgage-Related Investments that are not issued or guaranteed by government entities to 20% of its net assets. LMBS targets an estimated effective duration of three (3) years or less. LMBS may also invest in mortgage dollar rolls, to-be-announced transactions and engage in short sales. LMBS may invest up to 20% of its net assets in securities rated below investment grade, which are also known as high yield securities or "junk" bonds. Additional information regarding LMBS, including its prospectus and most recent annual report, is available without charge by visiting www.ftportfolios.com/Retail/Etf/EtfFundNews.aspx?Ticker=LMBS. FTSL FTSL's primary investment objective is to provide high current income and its secondary investment objective is the preservation of capital. Under normal market conditions, FTSL seeks to outperform each of the Primary Index and Secondary Index (as defined below) by investing at least 80% of its net assets in first lien senior floating rate bank loans ("Senior Loans"). The S&P/LSTA U.S. Leveraged Loan 100 Index (the "Primary Index") is a market value-weighted index designed to measure the performance of the largest segment of the U.S. syndicated leveraged loan market. The Primary Index consists of 100 loan facilities drawn from a larger benchmark, the S&P/LSTA Leveraged Loan Index. The Markit iBoxx USD Liquid Leveraged Loan Index (the "Secondary Index") selects the 100 most liquid Senior Loans in the market. FTSL does not seek to track either the Primary or Secondary Index, but rather seeks to outperform each of the indices. It is anticipated that FTSL, in accordance with its principal investment strategies, will invest approximately 50% to 75% of its net assets in Senior Loans that are eligible for inclusion in and meet the liquidity thresholds of the Primary and/or the Secondary Indices at the time of investment. A Senior Loan is an advance or commitment of funds made by one or more banks or similar financial institutions to one or more corporations, partnerships or other business entities and typically pays interest at a floating or adjusting rate that is determined periodically at a designated premium above a base lending rate. FTSL may invest significantly in "covenant-lite" loans, which are loans issued with fewer restrictions on collateral, payment terms and level of income. FTSL invests in Senior Loans made predominantly to businesses operating in North America, but may also invest in Senior Loans made to businesses operating outside of North America. FTSL invests primarily in Senior Loans that are rated below investment grade, which are also known as high yield securities or "junk" bonds. FTSL may also invest up to 20% of its net assets in (1) non-Senior Loan debt securities, which may be fixed-rate or floating-rate income-producing securities, (2) warrants, U.S. and non-U.S. equity and equity-like positions and interests and other securities issued by or with respect to a borrower or its affiliates, and/or (3) securities of other investment companies. In addition, FTSL may invest up to 15% of its net assets in Senior Loans and/or other floating rate loans that are distressed or in default. Additional information regarding FTSL, including its prospectus and most recent annual report, is available without charge by visiting www.ftportfolios.com/Retail/Etf/EtfFundNews.aspx?Ticker=FTSL. The Fund is classified as "non-diversified" under the Investment Company Act of 1940, as amended (the "1940 Act").
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	You could lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency. There can be no assurance that the Fund's investment objectives will be achieved. The order of the below risk factors does not indicate the significance of any particular risk factor. ASSET-BACKED SECURITIES RISK. The Fund may invest in ETFs that hold asset-backed securities. Asset-backed securities are debt securities typically created by buying and pooling loans or other receivables other than mortgage loans and creating securities backed by those similar type assets. As with other debt securities, asset-backed securities are subject to credit risk, extension risk, interest rate risk, liquidity risk and valuation risk. These securities are generally not backed by the full faith and credit of the U.S. government and are subject to the risk of default on the underlying asset or loan, particularly during periods of economic downturn. The impairment of the value of collateral or other assets underlying an asset-backed security, such as a result of non-payment of loans or non-performance of underlying assets, may result in a reduction in the value of such asset-backed securities and losses to an underlying ETF. ASSET CONCENTRATION RISK. Since the Fund may be composed of a very small number of ETFs, the Fund's performance may be hurt disproportionately and significantly by the poor performance of those ETFs to which it has significant exposure. Asset concentration makes the Fund more susceptible to any single occurrence affecting the underlying ETFs and may subject the Fund to greater market risk than more diversified funds. AUTHORIZED PARTICIPANT CONCENTRATION RISK. Only an authorized participant may engage in creation or redemption transactions directly with the Fund. A limited number of institutions act as authorized participants for the Fund. To the extent that these institutions exit the business or are unable to proceed with creation and/or redemption orders and no other authorized participant steps forward to create or redeem, the Fund's shares may trade at a premium or discount to the Fund's net asset value and possibly face delisting. BANK LOANS RISK. The Fund may invest in ETFs that hold bank loans. Investments in bank loans are subject to the same risks as investments in other types of debt securities, including credit risk, interest rate risk, liquidity risk and valuation risk that may be heightened because of the limited public information available regarding bank loans and because loan borrowers may be leveraged and tend to be more adversely affected by changes in market or economic conditions. If an underlying ETF holds a bank loan through another financial institution or relies on a financial institution to administer the loan, its receipt of principal and interest on the loan may be subject to the credit risk of that financial institution. It is possible that any collateral securing a loan may be insufficient or unavailable to the underlying ETF, and that the underlying ETF's rights to collateral may be limited by bankruptcy or insolvency laws. Additionally, there is no central clearinghouse for loan trades and the loan market has not established enforceable settlement standards or remedies for failure to settle. As such, the secondary market for bank loans may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods (in some cases longer than 7 days) which may cause the underlying ETF to be unable to realize the full value of its investment. In addition, bank loans are generally not registered with the Securities Exchange Commission under the Securities Act of 1933, as amended, and may not be considered "securities," and an underlying ETF may not be entitled to rely on the anti-fraud protections of the federal securities laws. CALL RISK. The Fund may invest in ETFs that hold debt securities. Some debt securities may be redeemed, or "called," at the option of the issuer before their stated maturity date. In general, an issuer will call its debt securities if they can be refinanced by issuing new debt securities which bear a lower interest rate. The underlying ETF is subject to the possibility that during periods of falling interest rates an issuer will call its high yielding debt securities. The underlying ETF would then be forced to invest the proceeds at lower interest rates, likely resulting in a decline in the ETF's income. COUNTERPARTY RISK. Fund transactions involving a counterparty are subject to the risk that the counterparty will not fulfill its obligation to the Fund. Counterparty risk may arise because of the counterparty's financial condition (i.e., financial difficulties, bankruptcy, or insolvency), market activities and developments, or other reasons, whether foreseen or not. A counterparty's inability to fulfill its obligation may result in significant financial loss to the Fund. The Fund may be unable to recover its investment from the counterparty or may obtain a limited recovery, and/or recovery may be delayed. COVENANT-LITE LOAN RISK. The Fund may invest in ETFs that hold covenant-lite loans. Covenant-lite loans contain fewer maintenance covenants, or no maintenance covenants at all, than traditional loans and may not include terms that allow the lender to monitor the financial performance of the borrower and declare a default if certain criteria are breached. This may hinder the underlying ETF's ability to reprice credit risk associated with the borrower and reduce the ETF's ability to restructure a problematic loan and mitigate potential loss. As a result, the underlying ETF's exposure to losses on such investments is increased, especially during a downturn in the credit cycle. CREDIT RISK. An issuer or other obligated party of a debt security held by an underlying ETF may be unable or unwilling to make dividend, interest and/or principal payments when due. In addition, the value of a debt security may decline because of concerns about the issuer's ability or unwillingness to make such payments. CURRENCY RISK. The Fund may invest in ETFs that hold securities denominated in a non-U.S. currency. Changes in currency exchange rates affect the value of investments denominated in a foreign currency, and therefore the value of such investments in an underlying ETF's portfolio. An underlying ETF's net asset value could decline if a currency to which an underlying ETF has exposure depreciates against the U.S. dollar or if there are delays or limits on repatriation of such currency. Currency exchange rates can be very volatile and can change quickly and unpredictably. As a result, the value of an investment in such an underlying ETF may change quickly and without warning. CYBER SECURITY RISK. The Fund is susceptible to operational risks through breaches in cyber security. A breach in cyber security refers to both intentional and unintentional events that may cause the Fund to lose proprietary information, suffer data corruption or lose operational capacity. Such events could cause the Fund to incur regulatory penalties, reputational damage, additional compliance costs associated with corrective measures and/or financial loss. Cyber security breaches may involve unauthorized access to the Fund's digital information systems through "hacking" or malicious software coding but may also result from outside attacks such as denial-of-service attacks through efforts to make network services unavailable to intended users. In addition, cyber security breaches of the issuers of securities in which the Fund invests or the Fund's third-party service providers, such as its administrator, transfer agent, custodian, or sub-advisor, as applicable, can also subject the Fund to many of the same risks associated with direct cyber security breaches. Although the Fund has established risk management systems designed to reduce the risks associated with cyber security, there is no guarantee that such efforts will succeed, especially because the Fund does not directly control the cyber security systems of issuers or third-party service providers. DEBT SECURITIES RISK. The Fund may invest in underlying ETFs that hold debt securities. Investments in debt securities subject the holder to the credit risk of the issuer. Credit risk refers to the possibility that the issuer or other obligor of a security will not be able or willing to make payments of interest and principal when due. Generally, the value of debt securities will change inversely with changes in interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. During periods of falling interest rates, the income received by an underlying ETF may decline. If the principal on a debt security is prepaid before expected, the prepayments of principal may have to be reinvested in obligations paying interest at lower rates. Debt securities generally do not trade on a securities exchange making them generally less liquid and more difficult to value than common stock. DEFAULTED SECURITIES RISK. The Fund may invest in ETFs that hold defaulted securities. Defaulted securities pose a greater risk that principal will not be repaid than non-defaulted securities. The reorganization or liquidation of an issuer of a defaulted security may result in an underlying ETF losing its entire investment or being required to accept cash or securities with a value less than its original investment. It may also be difficult to obtain complete and accurate information regarding the true financial condition of the issuer of a defaulted security. Defaulted securities and any securities received in an exchange for such securities may be subject to restrictions on resale. DISTRESSED SECURITIES RISK. The Fund may invest in ETFs that hold distressed securities. Distressed debt securities are speculative and involve substantial risks in addition to the risks of investing in high-yield securities that are not in default. Generally, an underlying ETF will not receive interest payments from the distressed securities it holds, and there is a substantial risk that the principal will not be repaid. In any reorganization or liquidation proceeding related to a distressed debt security, an underlying ETF may lose its entire investment in the security. EMERGING MARKETS RISK. The Fund may invest in ETFs that hold investments in securities issued by companies operating in emerging market countries. Investments in securities issued by companies operating in emerging market countries involve additional risks relating to political, economic, or regulatory conditions not associated with investments in securities and instruments issued by U.S. companies or by companies operating in other developed market countries. Investments in emerging markets securities are generally considered speculative in nature and are subject to the following heightened risks: smaller market capitalization of securities markets which may suffer periods of relative illiquidity; significant price volatility; restrictions on foreign investment; possible repatriation of investment income and capital; rapid inflation; and currency convertibility issues. Emerging market countries also often have less uniformity in accounting and reporting requirements, unsettled securities laws, unreliable securities valuation and greater risk associated with custody of securities. Furthermore, investors may be required to register the proceeds of sales and future economic or political crises could lead to price controls, forced mergers, expropriation or confiscatory taxation, seizure, nationalization or creation of government monopolies. ETF RISK. Under certain market conditions, the Fund may invest in ETFs. The Fund's investment in shares of ETFs subjects it to the risks of owning the securities underlying the ETF, as well as the same structural risks faced by an investor purchasing shares of the Fund, including authorized participant concentration risk, market maker risk, premium/discount risk and trading issues risk. As a shareholder in another ETF, the Fund bears its proportionate share of the ETF's expenses, subjecting Fund shareholders to duplicative expenses. EXTENSION RISK. The Fund may invest in ETFs that hold debt securities. Extension risk is the risk that, when interest rates rise, certain obligations will be paid off by the issuer (or other obligated party) more slowly than anticipated, causing the value of these debt securities to fall. Rising interest rates tend to extend the duration of debt securities, making their market value more sensitive to changes in interest rates. The value of longer-term debt securities generally changes more in response to changes in interest rates than shorter-term debt securities. As a result, in a period of rising interest rates, securities may exhibit additional volatility and may lose value. FIXED-TO-FLOATING RATE SECURITIES RISK. The Fund may invest in ETFs that hold fixed-to-floating rate securities. Fixed-to-floating rate securities are securities that have an initial term with a fixed dividend rate and following this initial term bear a floating dividend rate. Securities which include a floating or variable interest rate component can be less sensitive to interest rate changes than securities with fixed interest rates, but may decline in value if their interest rates do not rise as much, or as quickly, as interest rates in general. Although floating rate preferred securities can be less sensitive to interest rate risk than fixed-rate preferred securities, they are subject to the risks applicable to preferred securities more generally. FLOATING RATE DEBT INSTRUMENTS RISK. The Fund may invest in ETFs that hold floating rate debt securities. Investments in floating rate debt instruments are subject to the same risks as investments in other types of debt securities, including credit risk, interest rate risk, liquidity risk and valuation risk. Floating rate debt instruments include debt securities issued by corporate and governmental entities, as well bank loans, mortgage-backed securities and asset-backed securities. Floating rate debt instruments are structured so that the security's coupon rate fluctuates based upon the level of a reference rate. Most commonly, the coupon rate of a floating rate debt instrument is set at the level of a widely followed interest rate, plus a fixed spread. As a result, the coupon on floating rate debt instrument will generally decline in a falling interest rate environment, causing an underlying ETF to experience a reduction in the income it receives from the instrument. A floating rate debt instrument's coupon rate resets periodically according to its terms. Consequently, in a rising interest rate environment, floating rate debt instruments with coupon rates that reset infrequently may lag behind the changes in market interest rates. Floating rate debt instruments may also contain terms that impose a maximum coupon rate the issuer will pay, regardless of the level of the reference rate. To the extent an underlying ETF invests in floating rate loans, such instruments may be subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the underlying ETF needs to liquidate such securities. It is possible that the collateral securing a floating rate loan may be insufficient or unavailable to the underlying ETF, and that the underlying ETF's rights to collateral may be limited by bankruptcy or insolvency laws. Additionally, floating rate loans may not be considered "securities" under federal securities laws, and purchasers, such as an underlying ETF, therefore may not be entitled to rely on the anti-fraud protections of the federal securities laws. HIGH YIELD SECURITIES RISK. The Fund may invest in ETFs that hold high yield securities. High yield securities, or "junk" bonds, are subject to greater market fluctuations, are less liquid and provide a greater risk of loss than investment grade securities, and therefore, are considered to be highly speculative. In general, high yield securities may have a greater risk of default than other types of securities and could cause income and principal losses for an underlying ETF. INCOME RISK. The Fund may invest in ETFs that hold debt securities. An underlying ETF's income may decline when interest rates fall or if there are defaults in its portfolio. This decline can occur because an underlying ETF may subsequently invest in lower-yielding securities as debt securities in its portfolio mature, are near maturity or are called, or the ETF otherwise needs to purchase additional debt securities. INFLATION RISK. Inflation risk is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the present value of the Fund's assets and distributions may decline. INTEREST RATE RISK. The Fund may invest in ETFs that hold debt securities. Interest rate risk is the risk that the value of the debt securities in an underlying ETF's portfolio will decline because of rising market interest rates. Interest rate risk is generally lower for shorter term debt securities and higher for longer-term debt securities. An underlying ETF may be subject to a greater risk of rising interest rates than would normally be the case due to the current period of historically low rates and the effect of potential government fiscal policy initiatives and resulting market reaction to those initiatives. Duration is a reasonably accurate measure of a debt security's price sensitivity to changes in interest rates and a common measure of interest rate risk. Duration measures a debt security's expected life on a present value basis, taking into account the debt security's yield, interest payments and final maturity. In general, duration represents the expected percentage change in the value of a security for an immediate 1% change in interest rates. For example, the price of a debt security with a three-year duration would be expected to drop by approximately 3% in response to a 1% increase in interest rates. Therefore, prices of debt securities with shorter durations tend to be less sensitive to interest rate changes than debt securities with longer durations. As the value of a debt security changes over time, so will its duration. LIBOR RISK. In 2012, regulators in the United States and the United Kingdom alleged that certain banks, including some banks serving on the panel for U.S. dollar LIBOR, engaged in manipulative acts in connection with their submissions to the British Bankers Association. Manipulation of the LIBOR rate-setting process would raise the risk to the Fund of being adversely impacted if the Fund received a payment based upon LIBOR and such manipulation of LIBOR resulted in lower resets than would have occurred had there been no manipulation. In 2017, the head of the United Kingdom's Financial Conduct Authority announced a desire to phase out the use of LIBOR by the end of 2021. There remains uncertainty regarding the future utilization of LIBOR and the nature of any replacement rate. As such, the potential effect of a transition away from LIBOR on the Fund or the financial instruments in which the Fund invests cannot yet be determined. LIQUIDITY RISK. The Fund may invest in ETFs with investments that may be subject to restrictions on resale, trade over-the-counter or in limited volume, or lack an active trading market. Accordingly, an underlying ETF may not be able to sell or close out of such investments at favorable times or prices (or at all), or at the prices approximating those at which the ETF currently values them. Illiquid securities may trade at a discount from comparable, more liquid investments and may be subject to wide fluctuations in market value. MANAGEMENT RISK. The Fund is subject to management risk because it is an actively managed portfolio. In managing the Fund's investment portfolio, the portfolio managers will apply investment techniques and risk analyses that may not produce the desired result. There can be no guarantee that the Fund will meet its investment objectives. MARKET MAKER RISK. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares due to a limited number of market markers. Decisions by market makers or authorized participants to reduce their role or step away from these activities in times of market stress could inhibit the effectiveness of the arbitrage process in maintaining the relationship between the underlying values of the Fund's portfolio securities and the Fund's market price. The Fund may rely on a small number of third-party market makers to provide a market for the purchase and sale of shares. Any trading halt or other problem relating to the trading activity of these market makers could result in a dramatic change in the spread between the Fund's net asset value and the price at which the Fund's shares are trading on the Exchange, which could result in a decrease in value of the Fund's shares. This reduced effectiveness could result in Fund shares trading at a discount to net asset value and also in greater than normal intraday bid-ask spreads for Fund shares. MARKET RISK. Market risk is the risk that a particular security, or shares of the Fund in general, may fall in value. Securities are subject to market fluctuations caused by such factors as economic, political, regulatory or market developments, changes in interest rates and perceived trends in securities prices. Shares of the Fund could decline in value or underperform other investments. MORTGAGE-RELATED SECURITIES RISK. The Fund may invest in ETFs that hold mortgage-related securities. Mortgage-related securities are subject to the same risks as investments in other types of debt securities, including credit risk, interest rate risk, liquidity risk and valuation risk. However, these investments make an underlying ETF more susceptible to adverse economic, political or regulatory events that affect the value of real estate. Mortgage-related securities are also significantly affected by the rate of prepayments and modifications of the mortgage loans underlying those securities, as well as by other factors such as borrower defaults, delinquencies, realized or liquidation losses and other shortfalls. Mortgage-related securities are particularly sensitive to prepayment risk, given that the term to maturity for mortgage loans is generally substantially longer than the expected lives of those securities. As the timing and amount of prepayments cannot be accurately predicted, the timing of changes in the rate of prepayments of the mortgage loans may significantly affect an underlying ETF's actual yield to maturity on any mortgage-related securities. Along with prepayment risk, mortgage-related securities are significantly affected by interest rate risk. MUNICIPAL SECURITIES RISK. The Fund may invest in ETFs that hold municipal securities. Issuers, including governmental issuers, may be unable to pay their obligations as they come due. The values of municipal securities that depend on a specific revenue source to fund their payment obligations may fluctuate as a result of actual or anticipated changes in the cash flows generated by the revenue source or changes in the priority of the municipal obligation to receive the cash flows generated by the revenue source. The values of municipal securities held by an underlying ETF may be adversely affected by local political and economic conditions and developments. Adverse conditions in an industry significant to a local economy could have a correspondingly adverse effect on the financial condition of local issuers. In addition, income from municipal securities held by an underlying ETF could be declared taxable because of, among other things, unfavorable changes in tax laws, adverse interpretations by the Internal Revenue Service or state tax authorities, or noncompliant conduct of an issuer or other obligated party. Loss of tax-exempt status may cause interest received and distributed to shareholders by an underlying ETF to be taxable and may result in a significant decline in the values of such municipal securities. NON-AGENCY SECURITIES RISK. The Fund may invest in ETFs that hold non-agency securities. Investments in asset-backed or mortgage-backed securities offered by non-governmental issuers, such as commercial banks, savings and loans, private mortgage insurance companies, mortgage bankers and other secondary market issuers are subject to additional risks. There are no direct or indirect government or agency guarantees of payments in loan pools created by non-government issuers. Securities issued by private issuers are subject to the credit risks of the issuers. An unexpectedly high rate of defaults on the loan pool may adversely affect the value of a non-agency security and could result in losses to the Fund. The risk of such defaults is generally higher in the case of pools that include subprime loans. Non-agency securities are often not traded on an exchange and there may be a limited market for the securities, especially when there is a perceived weakness in the mortgage and real estate market sectors. Without an active trading market, the non-agency mortgage-related securities held by the Fund may be particularly difficult to value because of the complexities involved in assessing the value of the underlying loans. NON-DIVERSIFICATION RISK. The Fund is classified as "non-diversified" under the 1940 Act. As a result, the Fund is only limited as to the percentage of its assets which may be invested in the securities of any one issuer by the diversification requirements imposed by the Internal Revenue Code of 1986, as amended. The Fund may invest a relatively high percentage of its assets in a limited number of issuers. As a result, the Fund may be more susceptible to a single adverse economic or regulatory occurrence affecting one or more of these issuers, experience increased volatility and be highly invested in certain issuers. NON-U.S. SECURITIES RISK. The Fund may invest in ETFs that hold non-U.S. securities. Non-U.S. securities are subject to higher volatility than securities of domestic issuers due to possible adverse political, social or economic developments, restrictions on foreign investment or exchange of securities, lack of liquidity, currency exchange rates, excessive taxation, government seizure of assets, different legal or accounting standards, and less government supervision and regulation of securities exchanges in foreign countries. PREMIUM/DISCOUNT RISK. The market price of the Fund's shares will generally fluctuate in accordance with changes in the Fund's net asset value as well as the relative supply of and demand for shares on the Exchange. The Fund's investment advisor cannot predict whether shares will trade below, at or above their net asset value because the shares trade on the Exchange at market prices and not at net asset value. Price differences may be due, in large part, to the fact that supply and demand forces at work in the secondary trading market for shares will be closely related, but not identical, to the same forces influencing the prices of the holdings of the Fund trading individually or in the aggregate at any point in time. However, given that shares can only be purchased and redeemed in Creation Units, and only to and from broker-dealers and large institutional investors that have entered into participation agreements (unlike shares of closed-end funds, which frequently trade at appreciable discounts from, and sometimes at premiums to, their net asset value), the Fund's investment advisor believes that large discounts or premiums to the net asset value of shares should not be sustained. PREPAYMENT RISK. The Fund may invest in ETFs that hold debt securities. Prepayment risk is the risk that the issuer of a debt security will repay principal prior to the scheduled maturity date. Debt securities allowing prepayment may offer less potential for gains during a period of declining interest rates, as an underlying ETF may be required to reinvest the proceeds of any prepayment at lower interest rates. These factors may cause the value of an investment in an underlying ETF to change. REPURCHASE AGREEMENT RISK. The Fund may invest in ETFs that utilize repurchase agreements. Repurchase agreements are subject to the risk of failure. If the Fund's counterparty defaults on its obligations and the Fund is delayed or prevented from recovering the collateral, or if the value of the collateral is insufficient, the Fund may realize a loss. RESTRICTED SECURITIES RISK. The Fund may invest in ETFs that hold restricted securities. Restricted securities are securities that cannot be offered for public resale unless registered under the applicable securities laws or that have a contractual restriction that prohibits or limits their resale. The Fund may be unable to sell a restricted security on short notice or may be able to sell them only at a price below current value. SENIOR LOAN RISK. Senior loans represent debt obligations of sub-investment grade corporate borrowers, similar to high yield bonds; however, senior loans are different from traditional high yield bonds in that senior loans are typically senior to other obligations of the borrower and generally secured by a lien on all or some portion of the assets of the borrower. The senior loan market has seen a significant increase in loans with weaker lender protections including, but not limited to, limited financial maintenance covenants or, in some cases, no financial maintenance covenants (i.e., "covenant-lite loans") that would typically be included in a traditional loan agreement and general weakening of other restrictive covenants applicable to the borrower such as limitations on incurrence of additional debt, restrictions on payments of junior debt or restrictions on dividends and distributions. Weaker lender protections such as the absence of financial maintenance covenants in a loan agreement and the inclusion of "borrower-favorable" terms may impact recovery values and/or trading levels of senior loans in the future. The absence of financial maintenance covenants in a loan agreement generally means that the lender may not be able to declare a default if financial performance deteriorates. This may hinder the Fund's ability to reprice credit risk associated with a particular borrower and reduce the Fund's ability to restructure a problematic loan and mitigate potential loss. As a result, the Fund's exposure to losses on investments in senior loans may be increased, especially during a downturn in the credit cycle or changes in market or economic conditions. Senior loans are also subject to the same risks as investments in other types of debt securities, including credit risk, interest rate risk, liquidity risk and valuation risk that may be heightened because of the limited public information available regarding senior loans. If the Fund holds a senior loan through another financial institution or relies on a financial institution to administer the loan, its receipt of principal and interest on the loan may be subject to the credit risk of that financial institution. Although senior loans are generally secured by specific collateral, there can be no assurance that liquidation of such collateral would satisfy the borrower's obligation in the event of non-payment of scheduled interest or principal or that such collateral could be readily liquidated. No active trading market may exist for certain senior loans, which may impair the ability of the Fund to realize full value in the event of the need to sell its position in a senior loan and which may make it difficult to accurately value senior loans. Lastly, senior loans may not be considered "securities," and the Fund may not be entitled to rely on the anti-fraud protections of the federal securities laws. SHORT SALES RISK. The Fund may invest in ETFs that engage in short sales. In connection with a short sale of a security or other instrument, an underlying ETF is subject to the risk that instead of declining, the price of the security or other instrument sold short will rise. If the price of the security or other instrument sold short increases between the date of the short sale and the date on which an underlying ETF replaces the security or other instrument borrowed to make the short sale, the underlying ETF will experience a loss, which is theoretically unlimited since there is a theoretically unlimited potential for the market price of a security or other instrument sold short to increase. In addition, as a series of an investment company registered under the 1940 Act, the Fund must segregate liquid assets, or engage in other measures to "cover" open positions with respect to short sales. The Fund may nonetheless incur significant losses on short sales even if they are covered. SIGNIFICANT EXPOSURE RISK. To the extent that the Fund invests a large percentage of its assets in a single asset class or the securities of issuers within the same country, state, region, industry or sector, an adverse economic, business or political development may affect the value of the Fund's investments more than if the Fund were more broadly diversified. A significant exposure makes the Fund more susceptible to any single occurrence and may subject the Fund to greater market risk than a fund that is more broadly diversified. SOVEREIGN DEBT SECURITIES RISK. The Fund may invest in ETFs that hold sovereign debt securities. Sovereign debt securities are issued or guaranteed by foreign governmental entities. Investments in such securities are subject to the risk that the relevant sovereign government or governmental entity may delay or refuse to pay interest or repay principal on its debt. Such delays or refusals may be due to cash flow problems, insufficient foreign currency reserves, political considerations, the size of its debt relative to the economy or the failure to put in place economic reforms required by the International Monetary Fund or other multilateral agencies. There is no legal process for collecting sovereign debt that is not repaid, nor are there bankruptcy proceedings through which all or part of the unpaid sovereign debt may be collected. TBA TRANSACTIONS RISK. The Fund may invest in ETFs that engage in TBA transactions. The Fund may purchase securities in TBA Transactions. In such a transaction, the purchase price of the securities is typically fixed at the time of the commitment, but delivery and payment can take place a month or more after the date of the commitment. At the time of delivery of the securities, the value may be more or less than the purchase or sale price. Purchasing securities in a TBA Transaction may give rise to investment leverage and may increase the Fund's volatility. Default by, or bankruptcy of, a counterparty to a TBA Transaction would expose the Fund to possible losses because of an adverse market action, expenses or delays in connection with the purchase or sale of the pools specified in such transaction. TRADING ISSUES RISK. Although the shares of the Fund are listed for trading on the Exchange, there can be no assurance that an active trading market for such shares will develop or be maintained. Further, secondary markets may be subject to irregular trading activity and wide bid-ask spreads (which may be especially pronounced for smaller funds). Trading in shares on the Exchange may be halted due to market conditions or for reasons that, in the view of the Exchange, make trading in shares inadvisable. In addition, trading in shares on the Exchange is subject to trading halts caused by extraordinary market volatility pursuant to the Exchange's "circuit breaker" rules. Market makers are under no obligation to make a market in the Fund's shares, and authorized participants are not obligated to submit purchase or redemption orders for Creation Units. In the event market makers cease making a market in the Fund's shares or authorized participants stop submitting purchase or redemption orders for Creation Units, Fund shares may trade at a larger premium or discount to their net asset value. There can be no assurance that the requirements of the Exchange necessary to maintain the listing of the Fund will continue to be met or will remain unchanged. The Fund may have difficulty maintaining its listing on the Exchange in the event the Fund's assets are small or the Fund does not have enough shareholders. U.S. GOVERNMENT SECURITIES RISK. U.S. government securities are subject to interest rate risk but generally do not involve the credit risks associated with investments in other types of debt securities. As a result, the yields available from U.S. government securities are generally lower than the yields available from other debt securities. U.S. government securities are guaranteed only as to the timely payment of interest and the payment of principal when held to maturity. While securities issued or guaranteed by U.S. federal government agencies (such as Ginnie Mae) are backed by the full faith and credit of the U.S. Department of the Treasury, securities issued by government sponsored entities (such as Fannie Mae and Freddie Mac) are solely the obligation of the issuer and generally do not carry any guarantee from the U.S. government. VALUATION RISK. Unlike publicly traded securities that trade on national securities exchanges, there is no central place or exchange for trading most debt securities. Debt securities generally trade on an "over-the-counter" market. Due to the lack of centralized information and trading, the valuation of debt securities may carry more uncertainty and risk than that of publicly traded securities. Accordingly, determinations of the fair value of debt securities may be based on infrequent and dated information. Also, because the available information is less reliable and more subjective, elements of judgment may play a greater role in valuation of debt securities than for other types of securities. VOLATILITY RISK. Volatility is the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. The Fund may invest in securities or financial instruments that exhibit more volatility than the market as a whole. Such exposures could cause the Fund's net asset value to experience significant increases or declines in value over short periods of time.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund has not yet operated for a full calendar year and, therefore, performance information is not included in this section of the prospectus. See "Total Return Information" for performance information regarding the Fund.
First Trust Low Duration Strategic Focus ETF \| First Trust Low Duration Strategic Focus ETF
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Management Fees	rr_ManagementFeesOverAssets	0.20%
Distribution and Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	none
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.62%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.82%
1 Year	rr_ExpenseExampleNoRedemptionYear01	$ 84
3 Years	rr_ExpenseExampleNoRedemptionYear03	262
5 Years	rr_ExpenseExampleNoRedemptionYear05	455
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,014

Label

Element

Value

Risk/Return:

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Registrant Name

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FIRST TRUST EXCHANGE-TRADED FUND VIII

Prospectus Date

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Jan. 02, 2020

First Trust Low Duration Strategic Focus ETF

Risk/Return:

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Risk/Return [Heading]

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Summary Information

Objective [Heading]

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Investment Objectives

Objective, Primary [Text Block]

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The First Trust Low Duration Strategic Focus ETF (the "Fund") seeks to generate current income, with a secondary objective of preservation of capital.

Expense [Heading]

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Fees and Expenses of the Fund

Expense Narrative [Text Block]

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The following table describes the fees and expenses you may pay if you buy and hold shares of the Fund. Investors purchasing and selling shares may be subject to costs (including customary brokerage commissions) charged by their broker, which are not reflected in the table below.

Shareholder Fees Caption [Text]

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Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal period January 3, 2019 (inception) through August 31, 2019, the Fund's portfolio turnover rate was 14% of the average value of its portfolio.

Portfolio Turnover, Rate

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14.00%

Expense Example [Heading]

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Example

Expense Example, No Redemption Narrative [Text Block]

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The example below is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. This example does not take into account customary brokerage commissions that you pay when purchasing or selling shares of the Fund in the secondary market.

The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain at current levels. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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Under normal market conditions, the Fund seeks to achieve its investment objectives by investing at least 80% of its net assets (including investment borrowings) in a portfolio of U.S.-listed exchange-traded funds ("ETFs") that principally invest in income-generating securities that provide the Fund with an effective portfolio duration of three years or less. Duration is a measure of the expected price volatility of a debt security as a result of changes in market rates of interest, based on, among other factors, the weighted average timing of the debt security's expected principal and interest payments. In general, duration represents the expected percentage change in the value of a security for an immediate 1% change in interest rates. For example, the price of a security with a three-year duration would be expected to drop by approximately 3% in response to a 1% increase in interest rates.

In selecting the ETFs in which the Fund invests, First Trust Advisors L.P., the Fund's investment advisor ("First Trust"), uses a disciplined process for reviewing the macroeconomic outlook, policy drivers and asset level analysis that inform portfolio construction and ongoing risk management. The process begins with a robust, top-down review of macroeconomic factors including monetary and fiscal policies, growth forecasts, trade and tax policies, global market views and current market valuations. The process combines these factors with disciplined bottom-up asset level analysis including views on rates, duration, credit, currency and current asset valuations. First Trust utilizes this process to evaluate the relative attractiveness of the various fixed income asset classes in an attempt to best position the Fund to take advantage of market trends and investment opportunities. Lastly, First Trust seeks to construct a portfolio that provides the target effective duration of three years or less while managing both interest rate risk and credit risk.

A significant portion of the ETFs in which the Fund invests may be advised by First Trust. The Fund may invest in ETFs that invest principally in corporate bonds, floating rate loans and fixed-to-floating rate loans, senior loans, mortgage-backed securities, hybrid income securities (including convertible, contingent convertible and preferred securities), government debt and other fixed income securities. The securities to which the Fund may have exposure may be issued by both U.S. and non-U.S. issuers, including both corporate and governmental issuers located in countries considered to be emerging markets. The Fund may also invest up to 40% of its net assets in ETFs that have exposure to U.S. corporate high yield securities (also known as "junk bonds") and senior loans. The Fund may invest up to 20% of its net assets in bonds issued by non-U.S. government and corporate issuers, including up to 10% of its net assets in ETFs holding debt of issuers located in countries considered to be emerging markets. The Fund may also invest up to 10% of its net assets in ETFs holding preferred securities and up to 10% of its net assets in ETFs holding convertible securities.

The Fund invests significantly in the First Trust Enhanced Short Maturity ETF ("FTSM"), First Trust Low Duration Opportunities ETF ("LMBS") and First Trust Senior Loan Fund ("FTSL"). See below for a summary of FTSM's, LMBS's and FTSL's principal investment strategies.

FTSM

FTSM's investment objective is to seek current income, consistent with preservation of capital and daily liquidity. Under normal market conditions, FTSM intends to achieve its investment objective by investing at least 80% of its net assets in a portfolio of U.S. dollar-denominated fixed or floating rate debt securities, including securities issued or guaranteed by the U.S. government or its agencies, instrumentalities or U.S. government-sponsored entities, residential and commercial mortgage-backed securities, asset-backed securities, U.S. corporate bonds, fixed income securities issued by non-U.S. corporations and governments, municipal obligations and other debt securities bearing fixed or floating interest rates. FTSM may also invest in money market securities. FTSM may invest up to 20% of its net assets in privately-issued, non-agency sponsored mortgage- and asset-backed securities. Under normal market conditions, FTSM's portfolio is expected to have an average duration of less than one year and an average maturity of less than three years. Additional information regarding FTSM, including its prospectus and most recent annual report, is available without charge by visiting www.ftportfolios.com/Retail/Etf/EtfFundNews.aspx?Ticker=FTSM.

LMBS

LMBS's primary investment objective is to generate current income and its secondary investment objective is to provide capital appreciation. Under normal market conditions, LMBS seeks to achieve its investment objectives by investing at least 80% of its net assets in mortgage-related debt securities and other mortgage-related instruments (collectively, "Mortgage-Related Investments"). LMBS normally expects to invest in Mortgage-Related Investments tied to residential and commercial mortgages. Mortgage-Related Investments consist of: (1) residential mortgage-backed securities (RMBS); (2) commercial mortgage-backed securities (CMBS); (3) stripped mortgage-backed securities (SMBS), which are mortgage-backed securities where mortgage payments are divided up between paying the loan's principal and paying the loan's interest; and (4) collateralized mortgage obligations (CMOs) and real estate mortgage investment conduits (REMICs) where they are divided into multiple classes with each class being entitled to a different share of the principal and/or interest payments received from the pool of underlying assets. Mortgage-Related Investments typically represent an interest in a pool of mortgage loans made by banks and other financial institutions. The individual mortgage loans are packaged or "pooled" together for sale to investors. As the underlying mortgage loans are paid off, investors receive principal and interest payments. Mortgage-Related Investments may be fixed-rate or adjustable-rate Mortgage-Related Investments (ARMS). LMBS limits its investments in Mortgage-Related Investments that are not issued or guaranteed by government entities to 20% of its net assets. LMBS targets an estimated effective duration of three (3) years or less. LMBS may also invest in mortgage dollar rolls, to-be-announced transactions and engage in short sales. LMBS may invest up to 20% of its net assets in securities rated below investment grade, which are also known as high yield securities or "junk" bonds. Additional information regarding LMBS, including its prospectus and most recent annual report, is available without charge by visiting www.ftportfolios.com/Retail/Etf/EtfFundNews.aspx?Ticker=LMBS.

FTSL

FTSL's primary investment objective is to provide high current income and its secondary investment objective is the preservation of capital. Under normal market conditions, FTSL seeks to outperform each of the Primary Index and Secondary Index (as defined below) by investing at least 80% of its net assets in first lien senior floating rate bank loans ("Senior Loans"). The S&P/LSTA U.S. Leveraged Loan 100 Index (the "Primary Index") is a market value-weighted index designed to measure the performance of the largest segment of the U.S. syndicated leveraged loan market. The Primary Index consists of 100 loan facilities drawn from a larger benchmark, the S&P/LSTA Leveraged Loan Index. The Markit iBoxx USD Liquid Leveraged Loan Index (the "Secondary Index") selects the 100 most liquid Senior Loans in the market. FTSL does not seek to track either the Primary or Secondary Index, but rather seeks to outperform each of the indices. It is anticipated that FTSL, in accordance with its principal investment strategies, will invest approximately 50% to 75% of its net assets in Senior Loans that are eligible for inclusion in and meet the liquidity thresholds of the Primary and/or the Secondary Indices at the time of investment. A Senior Loan is an advance or commitment of funds made by one or more banks or similar financial institutions to one or more corporations, partnerships or other business entities and typically pays interest at a floating or adjusting rate that is determined periodically at a designated premium above a base lending rate. FTSL may invest significantly in "covenant-lite" loans, which are loans issued with fewer restrictions on collateral, payment terms and level of income. FTSL invests in Senior Loans made predominantly to businesses operating in North America, but may also invest in Senior Loans made to businesses operating outside of North America. FTSL invests primarily in Senior Loans that are rated below investment grade, which are also known as high yield securities or "junk" bonds. FTSL may also invest up to 20% of its net assets in (1) non-Senior Loan debt securities, which may be fixed-rate or floating-rate income-producing securities, (2) warrants, U.S. and non-U.S. equity and equity-like positions and interests and other securities issued by or with respect to a borrower or its affiliates, and/or (3) securities of other investment companies. In addition, FTSL may invest up to 15% of its net assets in Senior Loans and/or other floating rate loans that are distressed or in default. Additional information regarding FTSL, including its prospectus and most recent annual report, is available without charge by visiting www.ftportfolios.com/Retail/Etf/EtfFundNews.aspx?Ticker=FTSL.

The Fund is classified as "non-diversified" under the Investment Company Act of 1940, as amended (the "1940 Act").

Risk [Heading]

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Principal Risks

Risk Narrative [Text Block]

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You could lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency. There can be no assurance that the Fund's investment objectives will be achieved. The order of the below risk factors does not indicate the significance of any particular risk factor.

ASSET-BACKED SECURITIES RISK. The Fund may invest in ETFs that hold asset-backed securities. Asset-backed securities are debt securities typically created by buying and pooling loans or other receivables other than mortgage loans and creating securities backed by those similar type assets. As with other debt securities, asset-backed securities are subject to credit risk, extension risk, interest rate risk, liquidity risk and valuation risk. These securities are generally not backed by the full faith and credit of the U.S. government and are subject to the risk of default on the underlying asset or loan, particularly during periods of economic downturn. The impairment of the value of collateral or other assets underlying an asset-backed security, such as a result of non-payment of loans or non-performance of underlying assets, may result in a reduction in the value of such asset-backed securities and losses to an underlying ETF.

ASSET CONCENTRATION RISK. Since the Fund may be composed of a very small number of ETFs, the Fund's performance may be hurt disproportionately and significantly by the poor performance of those ETFs to which it has significant exposure. Asset concentration makes the Fund more susceptible to any single occurrence affecting the underlying ETFs and may subject the Fund to greater market risk than more diversified funds.

AUTHORIZED PARTICIPANT CONCENTRATION RISK. Only an authorized participant may engage in creation or redemption transactions directly with the Fund. A limited number of institutions act as authorized participants for the Fund. To the extent that these institutions exit the business or are unable to proceed with creation and/or redemption orders and no other authorized participant steps forward to create or redeem, the Fund's shares may trade at a premium or discount to the Fund's net asset value and possibly face delisting.

BANK LOANS RISK. The Fund may invest in ETFs that hold bank loans. Investments in bank loans are subject to the same risks as investments in other types of debt securities, including credit risk, interest rate risk, liquidity risk and valuation risk that may be heightened because of the limited public information available regarding bank loans and because loan borrowers may be leveraged and tend to be more adversely affected by changes in market or economic conditions. If an underlying ETF holds a bank loan through another financial institution or relies on a financial institution to administer the loan, its receipt of principal and interest on the loan may be subject to the credit risk of that financial institution. It is possible that any collateral securing a loan may be insufficient or unavailable to the underlying ETF, and that the underlying ETF's rights to collateral may be limited by bankruptcy or insolvency laws. Additionally, there is no central clearinghouse for loan trades and the loan market has not established enforceable settlement standards or remedies for failure to settle. As such, the secondary market for bank loans may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods (in some cases longer than 7 days) which may cause the underlying ETF to be unable to realize the full value of its investment. In addition, bank loans are generally not registered with the Securities Exchange Commission under the Securities Act of 1933, as amended, and may not be considered "securities," and an underlying ETF may not be entitled to rely on the anti-fraud protections of the federal securities laws.

CALL RISK. The Fund may invest in ETFs that hold debt securities. Some debt securities may be redeemed, or "called," at the option of the issuer before their stated maturity date. In general, an issuer will call its debt securities if they can be refinanced by issuing new debt securities which bear a lower interest rate. The underlying ETF is subject to the possibility that during periods of falling interest rates an issuer will call its high yielding debt securities. The underlying ETF would then be forced to invest the proceeds at lower interest rates, likely resulting in a decline in the ETF's income.

COUNTERPARTY RISK. Fund transactions involving a counterparty are subject to the risk that the counterparty will not fulfill its obligation to the Fund. Counterparty risk may arise because of the counterparty's financial condition (i.e., financial difficulties, bankruptcy, or insolvency), market activities and developments, or other reasons, whether foreseen or not. A counterparty's inability to fulfill its obligation may result in significant financial loss to the Fund. The Fund may be unable to recover its investment from the counterparty or may obtain a limited recovery, and/or recovery may be delayed.

COVENANT-LITE LOAN RISK. The Fund may invest in ETFs that hold covenant-lite loans. Covenant-lite loans contain fewer maintenance covenants, or no maintenance covenants at all, than traditional loans and may not include terms that allow the lender to monitor the financial performance of the borrower and declare a default if certain criteria are breached. This may hinder the underlying ETF's ability to reprice credit risk associated with the borrower and reduce the ETF's ability to restructure a problematic loan and mitigate potential loss. As a result, the underlying ETF's exposure to losses on such investments is increased, especially during a downturn in the credit cycle.

CREDIT RISK. An issuer or other obligated party of a debt security held by an underlying ETF may be unable or unwilling to make dividend, interest and/or principal payments when due. In addition, the value of a debt security may decline because of concerns about the issuer's ability or unwillingness to make such payments.

CURRENCY RISK. The Fund may invest in ETFs that hold securities denominated in a non-U.S. currency. Changes in currency exchange rates affect the value of investments denominated in a foreign currency, and therefore the value of such investments in an underlying ETF's portfolio. An underlying ETF's net asset value could decline if a currency to which an underlying ETF has exposure depreciates against the U.S. dollar or if there are delays or limits on repatriation of such currency. Currency exchange rates can be very volatile and can change quickly and unpredictably. As a result, the value of an investment in such an underlying ETF may change quickly and without warning.

CYBER SECURITY RISK. The Fund is susceptible to operational risks through breaches in cyber security. A breach in cyber security refers to both intentional and unintentional events that may cause the Fund to lose proprietary information, suffer data corruption or lose operational capacity. Such events could cause the Fund to incur regulatory penalties, reputational damage, additional compliance costs associated with corrective measures and/or financial loss. Cyber security breaches may involve unauthorized access to the Fund's digital information systems through "hacking" or malicious software coding but may also result from outside attacks such as denial-of-service attacks through efforts to make network services unavailable to intended users. In addition, cyber security breaches of the issuers of securities in which the Fund invests or the Fund's third-party service providers, such as its administrator, transfer agent, custodian, or sub-advisor, as applicable, can also subject the Fund to many of the same risks associated with direct cyber security breaches. Although the Fund has established risk management systems designed to reduce the risks associated with cyber security, there is no guarantee that such efforts will succeed, especially because the Fund does not directly control the cyber security systems of issuers or third-party service providers.

DEBT SECURITIES RISK. The Fund may invest in underlying ETFs that hold debt securities. Investments in debt securities subject the holder to the credit risk of the issuer. Credit risk refers to the possibility that the issuer or other obligor of a security will not be able or willing to make payments of interest and principal when due. Generally, the value of debt securities will change inversely with changes in interest rates. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. During periods of falling interest rates, the income received by an underlying ETF may decline. If the principal on a debt security is prepaid before expected, the prepayments of principal may have to be reinvested in obligations paying interest at lower rates. Debt securities generally do not trade on a securities exchange making them generally less liquid and more difficult to value than common stock.

DEFAULTED SECURITIES RISK. The Fund may invest in ETFs that hold defaulted securities. Defaulted securities pose a greater risk that principal will not be repaid than non-defaulted securities. The reorganization or liquidation of an issuer of a defaulted security may result in an underlying ETF losing its entire investment or being required to accept cash or securities with a value less than its original investment. It may also be difficult to obtain complete and accurate information regarding the true financial condition of the issuer of a defaulted security. Defaulted securities and any securities received in an exchange for such securities may be subject to restrictions on resale.

DISTRESSED SECURITIES RISK. The Fund may invest in ETFs that hold distressed securities. Distressed debt securities are speculative and involve substantial risks in addition to the risks of investing in high-yield securities that are not in default. Generally, an underlying ETF will not receive interest payments from the distressed securities it holds, and there is a substantial risk that the principal will not be repaid. In any reorganization or liquidation proceeding related to a distressed debt security, an underlying ETF may lose its entire investment in the security.

EMERGING MARKETS RISK. The Fund may invest in ETFs that hold investments in securities issued by companies operating in emerging market countries. Investments in securities issued by companies operating in emerging market countries involve additional risks relating to political, economic, or regulatory conditions not associated with investments in securities and instruments issued by U.S. companies or by companies operating in other developed market countries. Investments in emerging markets securities are generally considered speculative in nature and are subject to the following heightened risks: smaller market capitalization of securities markets which may suffer periods of relative illiquidity; significant price volatility; restrictions on foreign investment; possible repatriation of investment income and capital; rapid inflation; and currency convertibility issues. Emerging market countries also often have less uniformity in accounting and reporting requirements, unsettled securities laws, unreliable securities valuation and greater risk associated with custody of securities. Furthermore, investors may be required to register the proceeds of sales and future economic or political crises could lead to price controls, forced mergers, expropriation or confiscatory taxation, seizure, nationalization or creation of government monopolies.

ETF RISK. Under certain market conditions, the Fund may invest in ETFs. The Fund's investment in shares of ETFs subjects it to the risks of owning the securities underlying the ETF, as well as the same structural risks faced by an investor purchasing shares of the Fund, including authorized participant concentration risk, market maker risk, premium/discount risk and trading issues risk. As a shareholder in another ETF, the Fund bears its proportionate share of the ETF's expenses, subjecting Fund shareholders to duplicative expenses.

EXTENSION RISK. The Fund may invest in ETFs that hold debt securities. Extension risk is the risk that, when interest rates rise, certain obligations will be paid off by the issuer (or other obligated party) more slowly than anticipated, causing the value of these debt securities to fall. Rising interest rates tend to extend the duration of debt securities, making their market value more sensitive to changes in interest rates. The value of longer-term debt securities generally changes more in response to changes in interest rates than shorter-term debt securities. As a result, in a period of rising interest rates, securities may exhibit additional volatility and may lose value.

FIXED-TO-FLOATING RATE SECURITIES RISK. The Fund may invest in ETFs that hold fixed-to-floating rate securities. Fixed-to-floating rate securities are securities that have an initial term with a fixed dividend rate and following this initial term bear a floating dividend rate. Securities which include a floating or variable interest rate component can be less sensitive to interest rate changes than securities with fixed interest rates, but may decline in value if their interest rates do not rise as much, or as quickly, as interest rates in general. Although floating rate preferred securities can be less sensitive to interest rate risk than fixed-rate preferred securities, they are subject to the risks applicable to preferred securities more generally.

FLOATING RATE DEBT INSTRUMENTS RISK. The Fund may invest in ETFs that hold floating rate debt securities. Investments in floating rate debt instruments are subject to the same risks as investments in other types of debt securities, including credit risk, interest rate risk, liquidity risk and valuation risk. Floating rate debt instruments include debt securities issued by corporate and governmental entities, as well bank loans, mortgage-backed securities and asset-backed securities. Floating rate debt instruments are structured so that the security's coupon rate fluctuates based upon the level of a reference rate. Most commonly, the coupon rate of a floating rate debt instrument is set at the level of a widely followed interest rate, plus a fixed spread. As a result, the coupon on floating rate debt instrument will generally decline in a falling interest rate environment, causing an underlying ETF to experience a reduction in the income it receives from the instrument. A floating rate debt instrument's coupon rate resets periodically according to its terms. Consequently, in a rising interest rate environment, floating rate debt instruments with coupon rates that reset infrequently may lag behind the changes in market interest rates. Floating rate debt instruments may also contain terms that impose a maximum coupon rate the issuer will pay, regardless of the level of the reference rate. To the extent an underlying ETF invests in floating rate loans, such instruments may be subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the underlying ETF needs to liquidate such securities. It is possible that the collateral securing a floating rate loan may be insufficient or unavailable to the underlying ETF, and that the underlying ETF's rights to collateral may be limited by bankruptcy or insolvency laws. Additionally, floating rate loans may not be considered "securities" under federal securities laws, and purchasers, such as an underlying ETF, therefore may not be entitled to rely on the anti-fraud protections of the federal securities laws.

HIGH YIELD SECURITIES RISK. The Fund may invest in ETFs that hold high yield securities. High yield securities, or "junk" bonds, are subject to greater market fluctuations, are less liquid and provide a greater risk of loss than investment grade securities, and therefore, are considered to be highly speculative. In general, high yield securities may have a greater risk of default than other types of securities and could cause income and principal losses for an underlying ETF.

INCOME RISK. The Fund may invest in ETFs that hold debt securities. An underlying ETF's income may decline when interest rates fall or if there are defaults in its portfolio. This decline can occur because an underlying ETF may subsequently invest in lower-yielding securities as debt securities in its portfolio mature, are near maturity or are called, or the ETF otherwise needs to purchase additional debt securities.

INFLATION RISK. Inflation risk is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the present value of the Fund's assets and distributions may decline.

INTEREST RATE RISK. The Fund may invest in ETFs that hold debt securities. Interest rate risk is the risk that the value of the debt securities in an underlying ETF's portfolio will decline because of rising market interest rates. Interest rate risk is generally lower for shorter term debt securities and higher for longer-term debt securities. An underlying ETF may be subject to a greater risk of rising interest rates than would normally be the case due to the current period of historically low rates and the effect of potential government fiscal policy initiatives and resulting market reaction to those initiatives. Duration is a reasonably accurate measure of a debt security's price sensitivity to changes in interest rates and a common measure of interest rate risk. Duration measures a debt security's expected life on a present value basis, taking into account the debt security's yield, interest payments and final maturity. In general, duration represents the expected percentage change in the value of a security for an immediate 1% change in interest rates. For example, the price of a debt security with a three-year duration would be expected to drop by approximately 3% in response to a 1% increase in interest rates. Therefore, prices of debt securities with shorter durations tend to be less sensitive to interest rate changes than debt securities with longer durations. As the value of a debt security changes over time, so will its duration.

LIBOR RISK. In 2012, regulators in the United States and the United Kingdom alleged that certain banks, including some banks serving on the panel for U.S. dollar LIBOR, engaged in manipulative acts in connection with their submissions to the British Bankers Association. Manipulation of the LIBOR rate-setting process would raise the risk to the Fund of being adversely impacted if the Fund received a payment based upon LIBOR and such manipulation of LIBOR resulted in lower resets than would have occurred had there been no manipulation. In 2017, the head of the United Kingdom's Financial Conduct Authority announced a desire to phase out the use of LIBOR by the end of 2021. There remains uncertainty regarding the future utilization of LIBOR and the nature of any replacement rate. As such, the potential effect of a transition away from LIBOR on the Fund or the financial instruments in which the Fund invests cannot yet be determined.

LIQUIDITY RISK. The Fund may invest in ETFs with investments that may be subject to restrictions on resale, trade over-the-counter or in limited volume, or lack an active trading market. Accordingly, an underlying ETF may not be able to sell or close out of such investments at favorable times or prices (or at all), or at the prices approximating those at which the ETF currently values them. Illiquid securities may trade at a discount from comparable, more liquid investments and may be subject to wide fluctuations in market value.

MANAGEMENT RISK. The Fund is subject to management risk because it is an actively managed portfolio. In managing the Fund's investment portfolio, the portfolio managers will apply investment techniques and risk analyses that may not produce the desired result. There can be no guarantee that the Fund will meet its investment objectives.

MARKET MAKER RISK. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares due to a limited number of market markers. Decisions by market makers or authorized participants to reduce their role or step away from these activities in times of market stress could inhibit the effectiveness of the arbitrage process in maintaining the relationship between the underlying values of the Fund's portfolio securities and the Fund's market price. The Fund may rely on a small number of third-party market makers to provide a market for the purchase and sale of shares. Any trading halt or other problem relating to the trading activity of these market makers could result in a dramatic change in the spread between the Fund's net asset value and the price at which the Fund's shares are trading on the Exchange, which could result in a decrease in value of the Fund's shares. This reduced effectiveness could result in Fund shares trading at a discount to net asset value and also in greater than normal intraday bid-ask spreads for Fund shares.

MARKET RISK. Market risk is the risk that a particular security, or shares of the Fund in general, may fall in value. Securities are subject to market fluctuations caused by such factors as economic, political, regulatory or market developments, changes in interest rates and perceived trends in securities prices. Shares of the Fund could decline in value or underperform other investments.

MORTGAGE-RELATED SECURITIES RISK. The Fund may invest in ETFs that hold mortgage-related securities. Mortgage-related securities are subject to the same risks as investments in other types of debt securities, including credit risk, interest rate risk, liquidity risk and valuation risk. However, these investments make an underlying ETF more susceptible to adverse economic, political or regulatory events that affect the value of real estate. Mortgage-related securities are also significantly affected by the rate of prepayments and modifications of the mortgage loans underlying those securities, as well as by other factors such as borrower defaults, delinquencies, realized or liquidation losses and other shortfalls. Mortgage-related securities are particularly sensitive to prepayment risk, given that the term to maturity for mortgage loans is generally substantially longer than the expected lives of those securities. As the timing and amount of prepayments cannot be accurately predicted, the timing of changes in the rate of prepayments of the mortgage loans may significantly affect an underlying ETF's actual yield to maturity on any mortgage-related securities. Along with prepayment risk, mortgage-related securities are significantly affected by interest rate risk.

MUNICIPAL SECURITIES RISK. The Fund may invest in ETFs that hold municipal securities. Issuers, including governmental issuers, may be unable to pay their obligations as they come due. The values of municipal securities that depend on a specific revenue source to fund their payment obligations may fluctuate as a result of actual or anticipated changes in the cash flows generated by the revenue source or changes in the priority of the municipal obligation to receive the cash flows generated by the revenue source. The values of municipal securities held by an underlying ETF may be adversely affected by local political and economic conditions and developments. Adverse conditions in an industry significant to a local economy could have a correspondingly adverse effect on the financial condition of local issuers. In addition, income from municipal securities held by an underlying ETF could be declared taxable because of, among other things, unfavorable changes in tax laws, adverse interpretations by the Internal Revenue Service or state tax authorities, or noncompliant conduct of an issuer or other obligated party. Loss of tax-exempt status may cause interest received and distributed to shareholders by an underlying ETF to be taxable and may result in a significant decline in the values of such municipal securities.

NON-AGENCY SECURITIES RISK. The Fund may invest in ETFs that hold non-agency securities. Investments in asset-backed or mortgage-backed securities offered by non-governmental issuers, such as commercial banks, savings and loans, private mortgage insurance companies, mortgage bankers and other secondary market issuers are subject to additional risks. There are no direct or indirect government or agency guarantees of payments in loan pools created by non-government issuers. Securities issued by private issuers are subject to the credit risks of the issuers. An unexpectedly high rate of defaults on the loan pool may adversely affect the value of a non-agency security and could result in losses to the Fund. The risk of such defaults is generally higher in the case of pools that include subprime loans. Non-agency securities are often not traded on an exchange and there may be a limited market for the securities, especially when there is a perceived weakness in the mortgage and real estate market sectors. Without an active trading market, the non-agency mortgage-related securities held by the Fund may be particularly difficult to value because of the complexities involved in assessing the value of the underlying loans.

NON-DIVERSIFICATION RISK. The Fund is classified as "non-diversified" under the 1940 Act. As a result, the Fund is only limited as to the percentage of its assets which may be invested in the securities of any one issuer by the diversification requirements imposed by the Internal Revenue Code of 1986, as amended. The Fund may invest a relatively high percentage of its assets in a limited number of issuers. As a result, the Fund may be more susceptible to a single adverse economic or regulatory occurrence affecting one or more of these issuers, experience increased volatility and be highly invested in certain issuers.

NON-U.S. SECURITIES RISK. The Fund may invest in ETFs that hold non-U.S. securities. Non-U.S. securities are subject to higher volatility than securities of domestic issuers due to possible adverse political, social or economic developments, restrictions on foreign investment or exchange of securities, lack of liquidity, currency exchange rates, excessive taxation, government seizure of assets, different legal or accounting standards, and less government supervision and regulation of securities exchanges in foreign countries.

PREMIUM/DISCOUNT RISK. The market price of the Fund's shares will generally fluctuate in accordance with changes in the Fund's net asset value as well as the relative supply of and demand for shares on the Exchange. The Fund's investment advisor cannot predict whether shares will trade below, at or above their net asset value because the shares trade on the Exchange at market prices and not at net asset value. Price differences may be due, in large part, to the fact that supply and demand forces at work in the secondary trading market for shares will be closely related, but not identical, to the same forces influencing the prices of the holdings of the Fund trading individually or in the aggregate at any point in time. However, given that shares can only be purchased and redeemed in Creation Units, and only to and from broker-dealers and large institutional investors that have entered into participation agreements (unlike shares of closed-end funds, which frequently trade at appreciable discounts from, and sometimes at premiums to, their net asset value), the Fund's investment advisor believes that large discounts or premiums to the net asset value of shares should not be sustained.

PREPAYMENT RISK. The Fund may invest in ETFs that hold debt securities. Prepayment risk is the risk that the issuer of a debt security will repay principal prior to the scheduled maturity date. Debt securities allowing prepayment may offer less potential for gains during a period of declining interest rates, as an underlying ETF may be required to reinvest the proceeds of any prepayment at lower interest rates. These factors may cause the value of an investment in an underlying ETF to change.

REPURCHASE AGREEMENT RISK. The Fund may invest in ETFs that utilize repurchase agreements. Repurchase agreements are subject to the risk of failure. If the Fund's counterparty defaults on its obligations and the Fund is delayed or prevented from recovering the collateral, or if the value of the collateral is insufficient, the Fund may realize a loss.

RESTRICTED SECURITIES RISK. The Fund may invest in ETFs that hold restricted securities. Restricted securities are securities that cannot be offered for public resale unless registered under the applicable securities laws or that have a contractual restriction that prohibits or limits their resale. The Fund may be unable to sell a restricted security on short notice or may be able to sell them only at a price below current value.

SENIOR LOAN RISK. Senior loans represent debt obligations of sub-investment grade corporate borrowers, similar to high yield bonds; however, senior loans are different from traditional high yield bonds in that senior loans are typically senior to other obligations of the borrower and generally secured by a lien on all or some portion of the assets of the borrower. The senior loan market has seen a significant increase in loans with weaker lender protections including, but not limited to, limited financial maintenance covenants or, in some cases, no financial maintenance covenants (i.e., "covenant-lite loans") that would typically be included in a traditional loan agreement and general weakening of other restrictive covenants applicable to the borrower such as limitations on incurrence of additional debt, restrictions on payments of junior debt or restrictions on dividends and distributions. Weaker lender protections such as the absence of financial maintenance covenants in a loan agreement and the inclusion of "borrower-favorable" terms may impact recovery values and/or trading levels of senior loans in the future. The absence of financial maintenance covenants in a loan agreement generally means that the lender may not be able to declare a default if financial performance deteriorates. This may hinder the Fund's ability to reprice credit risk associated with a particular borrower and reduce the Fund's ability to restructure a problematic loan and mitigate potential loss. As a result, the Fund's exposure to losses on investments in senior loans may be increased, especially during a downturn in the credit cycle or changes in market or economic conditions.

Senior loans are also subject to the same risks as investments in other types of debt securities, including credit risk, interest rate risk, liquidity risk and valuation risk that may be heightened because of the limited public information available regarding senior loans. If the Fund holds a senior loan through another financial institution or relies on a financial institution to administer the loan, its receipt of principal and interest on the loan may be subject to the credit risk of that financial institution. Although senior loans are generally secured by specific collateral, there can be no assurance that liquidation of such collateral would satisfy the borrower's obligation in the event of non-payment of scheduled interest or principal or that such collateral could be readily liquidated.

No active trading market may exist for certain senior loans, which may impair the ability of the Fund to realize full value in the event of the need to sell its position in a senior loan and which may make it difficult to accurately value senior loans. Lastly, senior loans may not be considered "securities," and the Fund may not be entitled to rely on the anti-fraud protections of the federal securities laws.

SHORT SALES RISK. The Fund may invest in ETFs that engage in short sales. In connection with a short sale of a security or other instrument, an underlying ETF is subject to the risk that instead of declining, the price of the security or other instrument sold short will rise. If the price of the security or other instrument sold short increases between the date of the short sale and the date on which an underlying ETF replaces the security or other instrument borrowed to make the short sale, the underlying ETF will experience a loss, which is theoretically unlimited since there is a theoretically unlimited potential for the market price of a security or other instrument sold short to increase. In addition, as a series of an investment company registered under the 1940 Act, the Fund must segregate liquid assets, or engage in other measures to "cover" open positions with respect to short sales. The Fund may nonetheless incur significant losses on short sales even if they are covered.

SIGNIFICANT EXPOSURE RISK. To the extent that the Fund invests a large percentage of its assets in a single asset class or the securities of issuers within the same country, state, region, industry or sector, an adverse economic, business or political development may affect the value of the Fund's investments more than if the Fund were more broadly diversified. A significant exposure makes the Fund more susceptible to any single occurrence and may subject the Fund to greater market risk than a fund that is more broadly diversified.

SOVEREIGN DEBT SECURITIES RISK. The Fund may invest in ETFs that hold sovereign debt securities. Sovereign debt securities are issued or guaranteed by foreign governmental entities. Investments in such securities are subject to the risk that the relevant sovereign government or governmental entity may delay or refuse to pay interest or repay principal on its debt. Such delays or refusals may be due to cash flow problems, insufficient foreign currency reserves, political considerations, the size of its debt relative to the economy or the failure to put in place economic reforms required by the International Monetary Fund or other multilateral agencies. There is no legal process for collecting sovereign debt that is not repaid, nor are there bankruptcy proceedings through which all or part of the unpaid sovereign debt may be collected.

TBA TRANSACTIONS RISK. The Fund may invest in ETFs that engage in TBA transactions. The Fund may purchase securities in TBA Transactions. In such a transaction, the purchase price of the securities is typically fixed at the time of the commitment, but delivery and payment can take place a month or more after the date of the commitment. At the time of delivery of the securities, the value may be more or less than the purchase or sale price. Purchasing securities in a TBA Transaction may give rise to investment leverage and may increase the Fund's volatility. Default by, or bankruptcy of, a counterparty to a TBA Transaction would expose the Fund to possible losses because of an adverse market action, expenses or delays in connection with the purchase or sale of the pools specified in such transaction.

TRADING ISSUES RISK. Although the shares of the Fund are listed for trading on the Exchange, there can be no assurance that an active trading market for such shares will develop or be maintained. Further, secondary markets may be subject to irregular trading activity and wide bid-ask spreads (which may be especially pronounced for smaller funds). Trading in shares on the Exchange may be halted due to market conditions or for reasons that, in the view of the Exchange, make trading in shares inadvisable. In addition, trading in shares on the Exchange is subject to trading halts caused by extraordinary market volatility pursuant to the Exchange's "circuit breaker" rules. Market makers are under no obligation to make a market in the Fund's shares, and authorized participants are not obligated to submit purchase or redemption orders for Creation Units. In the event market makers cease making a market in the Fund's shares or authorized participants stop submitting purchase or redemption orders for Creation Units, Fund shares may trade at a larger premium or discount to their net asset value. There can be no assurance that the requirements of the Exchange necessary to maintain the listing of the Fund will continue to be met or will remain unchanged. The Fund may have difficulty maintaining its listing on the Exchange in the event the Fund's assets are small or the Fund does not have enough shareholders.

U.S. GOVERNMENT SECURITIES RISK. U.S. government securities are subject to interest rate risk but generally do not involve the credit risks associated with investments in other types of debt securities. As a result, the yields available from U.S. government securities are generally lower than the yields available from other debt securities. U.S. government securities are guaranteed only as to the timely payment of interest and the payment of principal when held to maturity. While securities issued or guaranteed by U.S. federal government agencies (such as Ginnie Mae) are backed by the full faith and credit of the U.S. Department of the Treasury, securities issued by government sponsored entities (such as Fannie Mae and Freddie Mac) are solely the obligation of the issuer and generally do not carry any guarantee from the U.S. government.

VALUATION RISK. Unlike publicly traded securities that trade on national securities exchanges, there is no central place or exchange for trading most debt securities. Debt securities generally trade on an "over-the-counter" market. Due to the lack of centralized information and trading, the valuation of debt securities may carry more uncertainty and risk than that of publicly traded securities. Accordingly, determinations of the fair value of debt securities may be based on infrequent and dated information. Also, because the available information is less reliable and more subjective, elements of judgment may play a greater role in valuation of debt securities than for other types of securities.

VOLATILITY RISK. Volatility is the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. The Fund may invest in securities or financial instruments that exhibit more volatility than the market as a whole. Such exposures could cause the Fund's net asset value to experience significant increases or declines in value over short periods of time.

Bar Chart and Performance Table [Heading]

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Performance

Performance Narrative [Text Block]

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The Fund has not yet operated for a full calendar year and, therefore, performance information is not included in this section of the prospectus. See "Total Return Information" for performance information regarding the Fund.

First Trust Low Duration Strategic Focus ETF | First Trust Low Duration Strategic Focus ETF

Risk/Return:

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Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

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none

Management Fees

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0.20%

Distribution and Service (12b-1) Fees

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none