Summary of Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited condensed consolidated financial statements included herein (the "Unaudited Condensed Consolidated Financial Statements") have been prepared by Criteo S.A. pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC"). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and the notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 2, 2020. The unaudited condensed consolidated financial statements included herein reflect all adjustments (consisting of normal, recurring adjustments) which are, in the opinion of management, necessary to state fairly the results for the interim periods presented. The results of operations for the interim periods presented are not necessarily indicative of the operating results to be expected for any subsequent interim period or for the fiscal year. Conformity with U.S. GAAP requires the use of estimates and judgments that affect the reported amounts of assets, liabilities, revenue and expenses in the condensed consolidated financial statements and accompanying notes. We base our estimates and judgments on historical information and on various other assumptions that we believe are reasonable under the circumstances. Our actual results may differ from these estimates. U.S. GAAP requires us to make estimates and judgments in several areas, including, but not limited to: (1) revenue recognition criteria, (2) allowances for credit losses, (3) research tax credits, (4) income taxes, including i) recognition of deferred tax assets arising from the subsidiaries projected taxable profit for future years, ii) evaluation of uncertain tax positions associated with our transfer pricing policy and iii) recognition of income tax position in respect with tax reforms recently enacted in countries we operate, (5) assumptions used in valuing acquired assets and assumed liabilities in business combinations, (6) assumptions used in the valuation of goodwill, intangible assets and right of use assets - operating lease, and (7) assumptions used in the valuation model to determine the fair value of share-based compensation plan. The ongoing impact of COVID-19 increases uncertainty associated with these estimates, in particular those related to allowance for credit losses, assumptions used in the valuation of goodwill and estimates relating to income taxes. There have been no changes to our significant accounting policies described in our Annual Report on Form 10-K for the fiscal year ended December 31, 2019, except for the accounting pronouncements adopted below
Recently Issued Accounting Standards	Accounting Pronouncements adopted in 2020 Effective January 1, 2020, we have adopted the Financial Accounting Standards Board ("FASB") Accounting Standards Update ("ASU") No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost. ASU 2016-13 replaces the existing incurred loss impairment model with an expected loss model which requires the use of forward-looking information to calculate credit loss estimates. This results in earlier recognition of credit losses. We measure loss allowances for all trade receivables using the lifetime expected credit loss approach, as described above. The expected credit losses on these financial assets are estimated using a provision matrix based on the Company’s historical credit loss experience, adjusted for factors that are specific to the debtors, general economic conditions and an assessment of both the current as well as the forecast direction of conditions at the reporting date. Effective January 1, 2020, we have adopted ASU 2017-04, Goodwill and Other (Topic 350). ASU 2017-04 simplifies the subsequent measurement of goodwill and reduces the cost and complexity of evaluating goodwill for impairment. It eliminates the need for entities to calculate the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination. Under this amendment, an entity will perform its goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An impairment charge is recognized for the amount by which the carrying value exceeds the reporting unit's fair value. The adoption of the ASU did not have an impact on our financial position or results of operations as we did not recognize an impairment loss during the period. Effective January 1, 2020, we have adopted ASU 2018-15, Intangibles - Goodwill and Other - Internal Use Software - Customer’s Accounting for Implementation Costs incurred in a Cloud Computing Arrangement That is a Service Contract. This ASU was issued to clarify the accounting for implementation costs incurred for SaaS agreements. Previously the guidance only referred to development of internal use software and the accounting for SaaS agreements was not clarified. This ASU states that the implementation costs of SaaS agreements should be capitalized. The adoption of the standard did not have an impact on our financial position or results of operations, however, it did have a minor impact on expense classification in current and future periods. Recent Accounting Pronouncements In August 2018, the FASB issued ASU 2018 - 14, Compensation - Retirement Benefits - Defined Benefit Plans - General. The purpose of this update is to modify disclosure requirements for Defined Benefit Plans. It removes requirements to disclose the amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit cost over the next fiscal year among others. It adds disclosure requirements for the items such as an explanation of the reasons for significant gains and losses related to changes in the benefit obligation for the period. We intend to adopt the standard on the effective date of January 1, 2021. The adoption of ASU 2018-14 is not expected to have a material impact on our financial position or results of operations but may have an impact on our disclosures. In December 2019, the FASB issued Accounting Standard Update No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12), which simplifies the accounting for income taxes. We intend to adopt the standard on the effective date of January 1, 2021. The adoption of ASU 2019-12 is not expected to have a material impact on our financial position or results of operations but may have an impact on our disclosures. Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s Consolidated Financial Statements upon adoption.
Revenue	Revenue Recognition We sell personalized display advertisements featuring product-level recommendations either directly to clients or to advertising agencies. Historically, the Criteo model has focused solely on converting our clients' website visitors into customers, enabling us to charge our clients only when users engage with an ad we deliver, usually by clicking on it. More recently, we have expanded our solutions to address a broader range of marketing goals for our clients. We offer two families of solutions to our commerce and brand clients: •Criteo Marketing Solutions allow commerce companies to address multiple marketing goals by engaging their consumers with personalized ads across the web, mobile and offline store environments. •Criteo Retail Media solutions allow retailers to generate advertising revenues from consumer brands, and/or to drive sales for themselves, by monetizing their data and audiences through personalized ads, either on their own digital property or on the open Internet, that address multiple marketing goals. In conjunction with broadening our solutions, we have also started expanding our pricing models to now include a combination of cost-per-install and cost-per-impression for selected new solutions, in addition to cost-per-click. We recognize revenues when we transfer control of promised services directly to our clients or to advertising agencies, which we collectively refer to as our clients, in an amount that reflects the consideration to which we expect to be entitled to in exchange for those services. For campaigns priced on a cost-per-click and cost-per-install basis, we bill our clients when a user clicks on an advertisement we deliver or installs an application by clicking on an advertisement we delivered, respectively. For these pricing models, we recognize revenue when a user clicks on an advertisement or installs an application. For campaigns priced on a cost-per-impression basis, we bill our clients based on the number of times an advertisement is displayed to a user. For this pricing model, we recognize revenue when an advertisement is displayed. We act as principal in our arrangements because (i) we control the advertising inventory (spaces on websites) before it is transferred to our clients; (ii) we bear sole responsibility for fulfillment of the advertising promise and inventory risks and (iii) we have full discretion in establishing prices. Therefore, based on these factors, we report revenue earned and the related costs incurred on a gross basis. Excluding our historical solution for driving Conversion as part of the Criteo Marketing Solutions family (formerly called Criteo Dynamic Retargeting), no individual solution from either the Criteo Marketing Solutions family, nor the Criteo Retail Media family, accounted for more than 10% of total consolidated revenue for the periods presented. Customer Credit Notes We offer credit notes to certain customers as a form of incentive, which are accounted for as variable consideration. We estimate these amounts based on the expected amount to be provided to customers and they are recognized as a reduction of revenue. We believe that there will not be significant changes to our estimates of variable consideration. Deferred Revenues We record deferred revenues when cash payments are received or due in advance of our performance. Our payment terms vary depending on the service or the type of customer. For certain customers, we require payment before the services are delivered. Practical Expedients We do not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which we recognize revenue at the amount to which we have the right to invoice for services performed. We generally expense sales commissions when incurred because the amortization period would have been one year or less. These costs are recorded within sales and operating expenses.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2020

The unaudited condensed consolidated financial statements included herein (the "Unaudited Condensed Consolidated Financial Statements") have been prepared by Criteo S.A. pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC"). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and the notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 2, 2020. The unaudited condensed consolidated financial statements included herein reflect all adjustments (consisting of normal, recurring adjustments) which are, in the opinion of management, necessary to state fairly the results for the interim periods presented. The results of operations for the interim periods presented are not necessarily indicative of the operating results to be expected for any subsequent interim period or for the fiscal year.

Conformity with U.S. GAAP requires the use of estimates and judgments that affect the reported amounts of assets, liabilities, revenue and expenses in the condensed consolidated financial statements and accompanying notes. We base our estimates and judgments on historical information and on various other assumptions that we believe are reasonable under the circumstances. Our actual results may differ from these estimates. U.S. GAAP requires us to make estimates and judgments in several areas, including, but not limited to: (1) revenue recognition criteria, (2) allowances for credit losses, (3) research tax credits, (4) income taxes, including i) recognition of deferred tax assets arising from the subsidiaries projected taxable profit for future years, ii) evaluation of uncertain tax positions associated with our transfer pricing policy and iii) recognition of income tax position in respect with tax reforms recently enacted in countries we operate, (5) assumptions used in valuing acquired assets and assumed liabilities in business combinations, (6) assumptions used in the valuation of goodwill, intangible assets and right of use assets - operating lease, and (7) assumptions used in the valuation model to determine the fair value of share-based compensation plan.

The ongoing impact of COVID-19 increases uncertainty associated with these estimates, in particular those related to allowance for credit losses, assumptions used in the valuation of goodwill and estimates relating to income taxes.

There have been no changes to our significant accounting policies described in our Annual Report on Form 10-K for the fiscal year ended December 31, 2019, except for the accounting pronouncements adopted below

Recently Issued Accounting Standards

Accounting Pronouncements adopted in 2020

Effective January 1, 2020, we have adopted the Financial Accounting Standards Board ("FASB") Accounting Standards Update ("ASU") No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost. ASU 2016-13 replaces the existing incurred loss impairment model with an expected loss model which requires the use of forward-looking information to calculate credit loss estimates. This results in earlier recognition of credit losses.

We measure loss allowances for all trade receivables using the lifetime expected credit loss approach, as described above. The expected credit losses on these financial assets are estimated using a provision matrix based on the Company’s historical credit loss experience, adjusted for factors that are specific to the debtors, general economic conditions and an assessment of both the current as well as the forecast direction of conditions at the reporting date.

Effective January 1, 2020, we have adopted ASU 2017-04, Goodwill and Other (Topic 350). ASU 2017-04 simplifies the subsequent measurement of goodwill and reduces the cost and complexity of evaluating goodwill for impairment. It eliminates the need for entities to calculate the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination. Under this amendment, an entity will perform its goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An impairment charge is recognized for the amount by which the carrying value exceeds the reporting unit's fair value. The adoption of the ASU did not have an impact on our financial position or results of operations as we did not recognize an impairment loss during the period.

Effective January 1, 2020, we have adopted ASU 2018-15, Intangibles - Goodwill and Other - Internal Use Software - Customer’s Accounting for Implementation Costs incurred in a Cloud Computing Arrangement That is a Service Contract. This ASU was issued to clarify the accounting for implementation costs incurred for SaaS agreements. Previously the guidance only referred to development of internal use software and the accounting for SaaS agreements was not clarified. This ASU states that the implementation costs of SaaS agreements should be capitalized. The adoption of the standard did not have an impact on our financial position or results of operations, however, it did have a minor impact on expense classification in current and future periods.

Recent Accounting Pronouncements

In August 2018, the FASB issued ASU 2018 - 14, Compensation - Retirement Benefits - Defined Benefit Plans - General. The purpose of this update is to modify disclosure requirements for Defined Benefit Plans. It removes requirements to disclose the amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit cost over the next fiscal year among others. It adds disclosure requirements for the items such as an explanation of the reasons for significant gains and losses related to changes in the benefit obligation for the period. We intend to adopt the standard on the effective date of January 1, 2021. The adoption of ASU 2018-14 is not expected to have a material impact on our financial position or results of operations but may have an impact on our disclosures.

In December 2019, the FASB issued Accounting Standard Update No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12), which simplifies the accounting for income taxes. We intend to adopt the standard on the effective date of January 1, 2021. The adoption of ASU 2019-12 is not expected to have a material impact on our financial position or results of operations but may have an impact on our disclosures.

Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s Consolidated Financial Statements upon adoption.

Revenue

Revenue Recognition

We sell personalized display advertisements featuring product-level recommendations either directly to clients or to advertising agencies. Historically, the Criteo model has focused solely on converting our clients' website visitors into customers, enabling us to charge our clients only when users engage with an ad we deliver, usually by clicking on it. More recently, we have expanded our solutions to address a broader range of marketing goals for our clients.

We offer two families of solutions to our commerce and brand clients:

•Criteo Marketing Solutions allow commerce companies to address multiple marketing goals by engaging their consumers with personalized ads across the web, mobile and offline store environments.

•Criteo Retail Media solutions allow retailers to generate advertising revenues from consumer brands, and/or to drive sales for themselves, by monetizing their data and audiences through personalized ads, either on their own digital property or on the open Internet, that address multiple marketing goals.

In conjunction with broadening our solutions, we have also started expanding our pricing models to now include a combination of cost-per-install and cost-per-impression for selected new solutions, in addition to cost-per-click.

We recognize revenues when we transfer control of promised services directly to our clients or to advertising agencies, which we collectively refer to as our clients, in an amount that reflects the consideration to which we expect to be entitled to in exchange for those services.

For campaigns priced on a cost-per-click and cost-per-install basis, we bill our clients when a user clicks on an advertisement we deliver or installs an application by clicking on an advertisement we delivered, respectively. For these pricing models, we recognize revenue when a user clicks on an advertisement or installs an application.

For campaigns priced on a cost-per-impression basis, we bill our clients based on the number of times an advertisement is displayed to a user. For this pricing model, we recognize revenue when an advertisement is displayed.

We act as principal in our arrangements because (i) we control the advertising inventory (spaces on websites) before it is transferred to our clients; (ii) we bear sole responsibility for fulfillment of the advertising promise and inventory risks and (iii) we have full discretion in establishing prices. Therefore, based on these factors, we report revenue earned and the related costs incurred on a gross basis.

Excluding our historical solution for driving Conversion as part of the Criteo Marketing Solutions family (formerly called Criteo Dynamic Retargeting), no individual solution from either the Criteo Marketing Solutions family, nor the Criteo Retail Media family, accounted for more than 10% of total consolidated revenue for the periods presented.

Customer Credit Notes

We offer credit notes to certain customers as a form of incentive, which are accounted for as variable consideration. We estimate these amounts based on the expected amount to be provided to customers and they are recognized as a reduction of revenue. We believe that there will not be significant changes to our estimates of variable consideration.

Deferred Revenues

We record deferred revenues when cash payments are received or due in advance of our performance. Our payment terms vary depending on the service or the type of customer. For certain customers, we require payment before the services are delivered.

Practical Expedients

We do not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which we recognize revenue at the amount to which we have the right to invoice for services performed.

We generally expense sales commissions when incurred because the amortization period would have been one year or less. These costs are recorded within sales and operating expenses.