Since it is implemented with a Runtime feature flag, it should be seen as the ServiceWorker registration does not have the backgroundFetch field. https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/modules/background_fetch/service_worker_registration_background_fetch.idl;l=12;drc=047c7dc4ee1ce908d7fea38ca063fa2f80f92c77
Then, they should be aware of the case as the lack of the field. 2025年11月25日(火) 17:46 Yoav Weiss (@Shopify) <[email protected]>: > What would breakage look like? I agree that usage is very low, but would > you expect users of those rare sites to be aware of breakage? Or would it > just prevent those sites from optimizing some flows? > > On Tue, Nov 25, 2025 at 5:41 AM Chromestatus < > [email protected]> wrote: > >> *Contact emails* >> [email protected] >> >> *Explainer* >> *No information provided* >> >> *Specification* >> https://wicg.github.io/background-fetch >> >> *Summary* >> Deprecates the Background Fetch API, which allows web applications to >> download large files in the background, even if the user navigates away >> from the page or closes the browser. Despite being available in Chrome >> since version 74, the Background Fetch API has not seen wide adoption by >> the developer community, with usage remaining consistently low, at less >> than 0.00002% of page loads as of November 2025. Given the low adoption >> rate and the significant engineering effort required to maintain the API >> and address ongoing security issues, it is being deprecated. Developers are >> encouraged to explore alternative solutions for managing large file >> downloads. >> >> *Blink component* >> Blink>ServiceWorker >> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EServiceWorker%22> >> >> *Web Feature ID* >> background-fetch <https://webstatus.dev/features/background-fetch> >> >> *Motivation* >> The Background Fetch API has been available in Chrome since version 74. >> However, it has not seen wide adoption. Usage metrics show that the feature >> is used in less than 0.00002% of page loads as of November 2025. Given the >> low usage, the ongoing engineering effort to maintain the Background Fetch >> API and address security issues is no longer justifiable. For developers >> who need to provide users with the ability to download large files, there >> are several alternatives: - For simple file downloads, developers can >> provide a standard download link. - For more advanced use cases, such as >> providing offline access to large files, developers can use the Fetch API >> within a Service Worker to download and cache the necessary resources. This >> approach provides developers with greater control over the user experience. >> >> *Initial public proposal* >> *No information provided* >> >> *TAG review* >> *No information provided* >> >> *TAG review status* >> Not applicable >> >> *Risks* >> >> >> *Interoperability and Compatibility* >> The interoperability risk of removing the Background Fetch API is low. >> The API has not been implemented by Firefox or Safari, and there have been >> no signals from either to indicate that they intend to do so. As a result, >> removing this API from Chrome will not cause interoperability issues, as it >> is not a feature that is part of the interoperable web platform. The >> compatibility risk is also minimal. Usage of the Background Fetch API has >> remained consistently low, at less than 0.00002% of page loads as of >> November 2025. Because of this extremely low usage, the number of websites >> that will be affected by this removal is very small. >> >> *Gecko*: No signal ( >> https://github.com/mozilla/standards-positions/issues/30) >> >> *WebKit*: No signal ( >> https://github.com/WebKit/standards-positions/issues/149) >> >> *Web developers*: No signals >> >> *Other signals*: TAG: https://github.com/w3ctag/design-reviews/issues/279 >> >> *Ergonomics* >> The Background Fetch API is tightly coupled with the Service Worker API. >> It is accessed through the backgroundFetch property of a >> ServiceWorkerRegistration object. Developers using this API would also >> likely use the Fetch API to create the Request objects for the download and >> the Cache API to store the downloaded responses. The API is designed to be >> asynchronous and to operate in the background. The main fetch() method >> returns a Promise, and the download process is managed by the browser, off >> the main thread. This design avoids blocking the main thread and is >> intended to improve performance and battery life for large downloads >> compared to keeping a service worker alive for a long-running fetch. >> Therefore, the API's usage does not inherently pose a performance risk that >> would make it difficult for Chrome to maintain good performance. The >> deprecation is due to low adoption and high maintenance cost, not because >> of ergonomic or performance issues in its design. >> >> *Activation* >> This change is a deprecation and removal of an existing API. The primary >> risk is the impact on developers who are currently using the Background >> Fetch API. However, the "activation" risk for this removal is minimal. The >> API has seen extremely low adoption since its introduction in Chrome 74, >> with usage below 0.00002% of page loads. This indicates that very few >> developers will be required to take action. >> >> *Security* >> The removal of the Background Fetch API reduces the overall attack >> surface of the browser and mitigates existing security issues associated >> with maintaining the feature. >> >> *WebView application risks* >> >> Does this intent deprecate or change behavior of existing APIs, such that >> it has potentially high risk for Android WebView-based applications? >> *No information provided* >> >> >> *Debuggability* >> *No information provided* >> >> *Will this feature be supported on all six Blink platforms (Windows, Mac, >> Linux, ChromeOS, Android, and Android WebView)?* >> No >> >> *Is this feature fully tested by web-platform-tests >> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?* >> No >> >> >> *Flag name on about://flags* >> *No information provided* >> >> *Finch feature name* >> BackgroundFetch >> >> *Rollout plan* >> Will ship enabled for all users >> >> *Requires code in //chrome?* >> False >> >> *Tracking bug* >> https://crbug.com/460293588 >> >> *Estimated milestones* >> Shipping on desktop 146 >> Shipping on Android 146 >> Shipping on WebView 146 >> >> *Anticipated spec changes* >> >> Open questions about a feature may be a source of future web compat or >> interop issues. Please list open issues (e.g. links to known github issues >> in the project for the feature specification) whose resolution may >> introduce web compat/interop risk (e.g., changing to naming or structure of >> the API in a non-backward-compatible way). >> *No information provided* >> >> *Link to entry on the Chrome Platform Status* >> https://chromestatus.com/feature/5074579353632768?gate=6606728540061696 >> >> This intent message was generated by Chrome Platform Status >> <https://chromestatus.com>. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "blink-dev" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6925253c.050a0220.107b62.0899.GAE%40google.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6925253c.050a0220.107b62.0899.GAE%40google.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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