Basis of Presentation and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 28, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	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	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 six months ended June 28, 2025 and June 29, 2024 each contained 26 weeks. Fiscal 2025 will end on December 27, 2025.
Fair Value	Whenever possible, the fair values of our financial assets and liabilities are determined using quoted market prices of identical securities or quoted market prices of similar securities from active markets. The three levels of inputs that may be used to measure fair value are as follows: •Level 1 valuations are obtained from real-time quotes for transactions in active exchange markets involving identical securities; •Level 2 valuations utilize significant observable inputs, such as quoted prices for similar assets or liabilities, quoted prices near the reporting date in markets that are less active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and •Level 3 valuations utilize unobservable inputs to the valuation methodology and include our own data about assumptions market participants would use in pricing the asset or liability based on the best information available under the circumstances. We did not have any transfers of assets or liabilities measured at fair value on a recurring basis to or from Level 1, Level 2 or Level 3 during the six months ended June 28, 2025 or the year ended December 28, 2024. The carrying values of Cash, Accounts receivable, net, Restricted cash, Prepaid expenses and other current assets, Accounts payable, and Accrued liabilities approximate fair value due to their short maturities. No changes were made to our valuation techniques during the first six months of fiscal 2025. Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis We measure and report our non-financial assets such as Property, plant and equipment, Equity investment, Goodwill and Intangible assets at fair value on a non-recurring basis if we determine these assets to be impaired or in the period when we make a business acquisition.
New Accounting Pronouncements	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, in tabular format, in the notes to the financial statements, specific information about certain costs and expenses. Although the ASU does not change the expense captions an entity presents on the face of the income statement, it requires disaggregation of certain expense captions into specified categories. 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. 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.