Basis of Presentation and Significant Accounting Policies	3 Months Ended
	Mar. 29, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies Basis of Presentation The accompanying condensed consolidated financial information of FormFactor, Inc. is unaudited and has been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). However, such information reflects all adjustments, consisting only of normal recurring adjustments, which are, in the opinion of management, necessary for a fair presentation of the financial position, results of operations and cash flows for the interim periods. The condensed consolidated financial statements included herein should be read in conjunction with the consolidated financial statements and the notes thereto included in our 2024 Annual Report on Form 10-K filed with the SEC on February 21, 2025. The results of operations for the interim periods presented are not necessarily indicative of the results to be expected for the full year. Fiscal Year We operate on a 52/53 week fiscal year, whereby the fiscal year ends on the last Saturday of December. Fiscal 2025 and 2024 each contain 52 weeks and the three months ended March 29, 2025 and March 30, 2024 each contained 13 weeks. Fiscal 2025 will end on December 27, 2025. Significant Accounting Policies Our significant accounting policies have not changed during the three months ended March 29, 2025 from those disclosed in our Annual Report on Form 10-K for the year ended December 28, 2024, except for: Equity Investment On February 21, 2025, Frontier Investments Co., Ltd (“HoldCo”), a joint holding company in which we hold a 20% share of the equity and an affiliate of MBK Partners holds an 80% share of the equity, through HoldCo’s wholly-owned subsidiary, FM Holdings Co., Ltd., acquired 100% of the shares of FICT Limited (“FICT”) from Advantage Partners Inc. Our investment of $67.2 million, comprises the funding of our share of the purchase price of $59.6 million, subject to changes in foreign currency fluctuations, and acquisition costs of $7.5 million. Headquartered in Nagano, Japan, FICT is a provider of semiconductor test and high-performance computing industries with complex multi-layer organic substrates, printed circuit boards, and related leading-edge technologies and services. This investment is accounted for as an equity method investment and recorded in Equity investment on our Condensed Consolidated Balance Sheets. We will report the results of our share of the investment with HoldCo on a one-quarter lag as their results are not expected to be available in time to be recorded in the concurrent period. During the three months ended March 29, 2025, we engaged in transactions with FICT, a related party. These transactions were conducted in the normal course of business and at arm's length. The total amount of these transactions was not material to our financial statements. New Accounting Pronouncements ASU 2024-03 In November 2024, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2024-03, “Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses.” This ASU requires an entity to disclose the amounts of purchases of inventory, employee compensation, depreciation, and intangible asset amortization included in each relevant expense caption. It also requires an entity to include certain amounts that are already required to be disclosed under current GAAP in the same disclosure. Additionally, it requires an entity to disclose a qualitative description of the amounts remaining in relevant expense captions that are not separately disaggregated quantitatively, and to disclose the total amount of selling expenses and, in annual reporting periods, an entity’s definition of selling expenses. The amendments in the ASU are effective for annual reporting periods beginning after December 15, 2026 and interim reporting periods beginning after December 15, 2027, with early adoption permitted. An entity may apply the amendments prospectively for reporting periods after the effective date or retrospectively to any or all prior periods presented in the financial statements. While this ASU will impact only our disclosures and not our financial condition and results of operations, we are currently evaluating the effect the adoption of this ASU may have on our disclosures. ASU 2023-09 In December 2023, the FASB issued ASU 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures.” The ASU includes requirements that an entity disclose specific categories in the rate reconciliation and provide additional information for reconciling items that are greater than five percent of the amount computed by multiplying pretax income by the applicable statutory income tax rate. The standard also requires that entities disclose income before income taxes and provision for income taxes disaggregated between domestic and foreign. This ASU is effective for annual periods beginning after December 15, 2024, with early adoption permitted. An entity may apply the amendments outlined in this ASU prospectively by providing the revised disclosures for the current period and continuing to provide the pre-ASU disclosures for the prior periods, or may apply the amendments retrospectively by providing the revised disclosures for all periods presented. We will adopt this ASU retrospectively for the period ending December 27, 2025, and it will impact only our disclosures with no impacts to our financial condition and results of operations.