Basis of Presentation and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. As such, the information included in this Form 10-Q should be read in conjunction with the consolidated financial statements and accompanying notes included in our final prospectus filed with the SEC on October 3, 2018 (the “Prospectus”) pursuant to Rule 424(b) under the Securities Act of 1933, as amended (the “Securities Act”). The condensed consolidated balance sheet as of December 31, 2017 included herein was derived from the audited financial statements as of that date, but does not include all disclosures including notes required by U.S. GAAP. The condensed consolidated financial statements include the accounts of Upwork Inc. and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated. The accompanying condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the financial position, results of operations, and cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full year ending December 31, 2018.
Initial Public Offering	Initial Public Offering In October 2018, the Company completed its initial public offering (the “IPO”), in which the Company issued and sold an aggregate of 7,840,908 shares of the Company’s common stock, including 1,022,727 shares pursuant to the exercise of the underwriters’ option to purchase additional shares, and selling stockholders sold 6,507,288 shares of the Company’s common stock, including 848,776 shares pursuant to the exercise of the underwriters’ option to purchase additional shares. The shares were sold at the IPO price of $15.00 per share. The Company received aggregate net proceeds of $109.4 million from the IPO after deducting underwriting discounts and commissions. Because the IPO closed in October 2018, the condensed consolidated financial statements as of September 30, 2018 and for the periods then ended, do not reflect the impact of the IPO. See Note 14—Subsequent Events.
Income Taxes	Income Taxes The Company recorded immaterial provision for income taxes in all periods presented. The Company continues to maintain a full valuation allowance against its net deferred tax assets. As of September 30, 2018, the Company had unrecognized tax benefits of $10.8 million, none of which would currently affect the Company’s effective tax rate if recognized due to the Company’s net deferred tax assets being fully offset by a valuation allowance. The Company does not anticipate that the amount of unrecognized tax benefits relating to tax positions existing at September 30, 2018 will significantly increase or decrease within the next 12 months. There was no interest expense or penalties related to unrecognized tax benefits recorded through September 30, 2018. A number of years may elapse before an uncertain tax position is audited and finally resolved. While it is often difficult to predict the final outcome or the timing of resolution of any particular uncertain tax position, the Company believes that its reserves for income taxes reflect the most likely outcome. The Company adjusts these reserves, as well as the related interest, in light of changing facts and circumstances. Settlement of any particular position would not require the use of cash. On December 22, 2017, the U.S. government enacted comprehensive tax legislation referred to as the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act significantly revises the future ongoing U.S. corporate income tax by, among other things, lowering the U.S. corporate income tax rates and implementing a territorial tax system. The corporate tax rate was reduced from 35% to 21% for tax years beginning after December 31, 2017 and certain provisions exist on which to allow accelerated expensing of equipment for a portion of 2017 and for future years. These changes primarily impacted the value of the Company’s deferred tax assets with a corresponding offset to valuation allowance, both of which were recognized in the year ended December 31, 2017. The Tax Act also limits the amount of net operating losses that can be used to reduce taxable income to 80% for net operating losses generated for periods beginning after December 31, 2017. Existing net operating losses, arising in years on or before December 31, 2017 are not affected by the Tax Act. The Company expects to finalize the assessment of the accounting for the income tax effects of the Tax Act, as it relates to its current structure, including provisions that are effective for tax years beginning in 2018 during the three months ended December 31, 2018. The Company’s preliminary assessment is subject to revisions to any additional guidance issued by the U.S. Treasury Department, the Internal Revenue Service, the Financial Accounting Standards Board (“FASB”), and other standard-setting and regulatory bodies. Adjustments may materially impact the Company’s provision for income taxes and the assessment of the accounting for the tax effects of the Tax Act will not extend beyond one year from the enactment date.
Significant Accounting Policies	Significant Accounting Policies There have been no changes to the Company’s significant accounting policies that are described in the Prospectus.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make certain estimates, judgments, and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expenses during the periods presented. Such estimates include, but are not limited to, the useful lives of assets; assessment of the recoverability of long-lived assets; goodwill impairment; allowance for doubtful accounts; liabilities relating to transaction losses; the valuation of warrants; stock-based compensation; and accounting for income taxes. Management bases its estimates on historical experience and on various other assumptions that management believes to be reasonable under the circumstances. The Company evaluates its estimates, assumptions, and judgments on an ongoing basis using historical experience and other factors and revises them when facts and circumstances dictate. Actual results could materially differ from these estimates.
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted As an “emerging growth company,” the Jumpstart Our Business Startups Act (“JOBS Act”) allows the Company to delay adoption of new or revised accounting pronouncements applicable to public companies until such pronouncements are made applicable to private companies. The Company has elected to use this extended transition period under the JOBS Act. The adoption dates discussed below reflect this election. In May 2014, the FASB issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (“ASC 606”). ASC 606 supersedes the revenue recognition requirements in ASC 605, and requires the recognition of revenue when promised goods or services are transferred to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASC 606 also includes Subtopic 340-40, Other Assets and Deferred Costs—Contracts with Customers (“Subtopic 340-40” and together with ASC 606, the “new revenue standard”), which requires the deferral of incremental costs of obtaining a contract with a customer. In August 2015, the FASB deferred the effective date for annual reporting periods beginning after December 15, 2017. In 2016, the FASB issued amendments on this guidance with the same effective date and transition guidance. The new revenue standard may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The Company is required to adopt the new revenue standard for the year ending December 31, 2019. Interim reporting under ASC 606 will not be required until 2020. To date, the Company has established an implementation team and is in the process of evaluating the impact of the new revenue standard on its accounting policies, processes, and system requirements. Furthermore, the Company has made and will continue to make investments in systems to enable timely and accurate reporting under the new revenue standard. The Company is continuing to evaluate adoption methods and the potential impact that the implementation of this standard will have on its condensed consolidated financial statements, including the identification of performance obligations, evaluation of material right considerations, principal agent considerations, the timing of revenue recognition, and related disclosures, but has not yet determined whether the effects of adoption will be material to its condensed consolidated financial statements. In February 2016, FASB issued ASU No. 2016-02, Leases (Topic 842), related to how an entity should recognize lease assets and lease liabilities. The guidance specifies that an entity that is a lessee under lease agreements should recognize lease assets and lease liabilities for those leases classified as operating leases under previous FASB guidance. Accounting for leases by lessors is largely unchanged under the new guidance. In 2018, the FASB also approved an amendment that would permit the option to adopt the new standard prospectively as of the effective date, without adjusting comparative periods presented. The new standard becomes effective for the Company for the year ending on December 31, 2020. The Company is currently evaluating the impact of adopting this new guidance on its condensed consolidated financial statements. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payment, to clarify how certain cash receipts and payments are presented and classified in the statement of cash flows. The new guidance becomes effective for the Company for the year ending December 31, 2019, although early adoption is permitted. The Company is currently evaluating the impact of adopting this new guidance on its condensed consolidated financial statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash, that will require that the amounts generally described as restricted cash and restricted cash equivalents would be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period amounts shown on the statement of cash flows. The new guidance also requires certain disclosures to supplement the statement of cash flows. The guidance becomes effective for the Company for the year ending on December 31, 2019, although early adoption is permitted. The Company is currently evaluating the impact of adopting this new guidance on its condensed consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-04, Intangibles—Goodwill and Others (Topic 350): Simplifying the Test for Goodwill Impairment. ASU No. 2017-04 eliminates Step 2 from the goodwill impairment test, which measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. Under ASU No. 2017-04, an entity should perform its annual or interim goodwill impairment test by comparing the fair value of the reporting unit with its carrying amount and recognize an impairment loss for the amount by which the carrying amount exceeds the reporting unit’s fair value, with the loss not exceeding the total amount of goodwill allocated to that reporting unit. The guidance becomes effective for the Company on a prospective basis for its annual or any interim goodwill impairment tests during the year ending on December 31, 2021, although early adoption is permitted. The Company is currently evaluating the impact of adopting this new guidance on its condensed consolidated financial statements. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, which expands and refines hedge accounting for both financial and non-financial risk components, aligns the recognition and presentation of the effects of hedging instruments and hedge items in the financial statements, and includes certain targeted improvements to ease the application of current guidance related to the assessment of hedge effectiveness. ASU No. 2017-12 is effective for the Company for fiscal years beginning after December 15, 2019. Early adoption is permitted. The Company has not yet evaluated the impact of this standard on its financial statements and related disclosures. In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. ASU No. 2018-07 expands the scope of Topic 718, Compensation-Stock Compensation to include share-based payment transactions for acquiring goods and services from non-employees. These awards are measured at the grant-date fair value of the equity instruments that an entity is obligated to issue when the good has been delivered or the service has been rendered and any other conditions necessary to earn the right to benefit from the instruments have been satisfied. The guidance is effective for the Company for the fiscal year ending on December 31, 2020, although early adoption is permitted but not earlier than the Company’s adoption of ASC 606, and the guidance requires a modified retrospective application to awards that have not been settled as of the adoption date. The Company has not yet evaluated the impact of this standard on its financial statements and related disclosures. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement, which modifies the disclosure requirements on fair value measurements. ASU No. 2018-13 is effective for the Company for the fiscal year ending on December 31, 2021, although early adoption is permitted. The Company has not yet evaluated the impact of this standard on its financial statements and related disclosures. In August 2018, the FASB issued ASU No. 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 aligns the requirements for capitalizing implementation costs in a cloud computing arrangement service contract with the requirements for capitalizing implementation costs incurred for an internal-use software license. ASU No. 2018-15 is effective for the Company for the fiscal year ending on December 31, 2021, although early adoption is permitted. The Company has not yet evaluated the impact of this standard on its financial statements and related disclosures.
Recently Adopted Accounting Pronouncement	Recently Adopted Accounting Pronouncement In March 2016, the FASB issued ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The Company adopted this standard as of January 1, 2018. ASU 2016-09 eliminates the requirement to delay the recognition of excess tax benefits until they reduce current taxes payable. Under this standard, previously unrecognized excess tax benefits shall be recognized on a modified retrospective basis. ASU No. 2016-09 also requires excess tax benefits and deficiencies to be recognized prospectively in the Company’s provision for income taxes rather than additional paid-in capital. Additionally, the Company elected to account for forfeitures as they occur rather than estimate expected forfeiture using a modified retrospective transition method. Finally, ASU No. 2016-09 requires excess tax benefits to be presented as a component of operating cash flows rather than financing cash flows. The Company elected to adopt this requirement prospectively and accordingly, prior periods have not been adjusted. The adoption of this standard was immaterial to the condensed consolidated financial statements as of and for the three and nine months ended September 30, 2018. In May 2017, the FASB issued ASU 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting, which provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in the ASU. The Company adopted this standard as of January 1, 2018. The adoption of this standard had no impact on the Company’s condensed consolidated financial statements as of and for the three and nine months ended September 30, 2018.

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.