Summary of significant accounting policies (Policies)	3 Months Ended
Summary of significant accounting policies (Policies)	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of presentation	The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America, or U.S. GAAP, and applicable rules and regulations of the Securities and Exchange Commission, or the SEC, regarding interim financial reporting, and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements.
Consolidation	These condensed consolidated financial statements include the accounts of C4 Therapeutics, Inc. and its subsidiary, C4T Securities Corporation. All intercompany balances and transactions have been eliminated in consolidation.
Unaudited interim financial information	Unaudited interim financial information The accompanying condensed consolidated balance sheet as of March 31, 2024, the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2024 and 2023, the condensed consolidated statements of stockholders’ equity for the three months ended March 31, 2024 and 2023, and the condensed consolidated statements of cash flows for the three months ended March 31, 2024 and 2023, and the related interim disclosures are unaudited. These unaudited condensed consolidated financial statements include all adjustments necessary, consisting of only normal recurring adjustments, to fairly state the financial position and the results of the Company’s operations and cash flows for interim periods in accordance with U.S. GAAP. Interim period results are not necessarily indicative of results of operations or cash flows for a full year or any subsequent interim period. The accompanying condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements as of and for year ended December 31, 2023, and notes thereto, which are included in the Company’s 2023 Annual Report on Form 10-K that was filed with the SEC on February 22, 2024, or the 2023 Annual Report.
Use of estimates	Use of estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. This process may result in actual results differing materially from those estimated amounts used in the preparation of the condensed consolidated financial statements if these results differ from historical experience or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, amounts and timing of revenues recognized under the Company’s research and development collaboration arrangements, prepaid and accrued research and development expense, incremental borrowing rate used in the measurement of lease liabilities, and estimated volatility used in fair valuation of stock options. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates.