FetchEvent.handled

Category: Service Worker
Type: New or changed feature
Status: Enabled by default (Chrome 86)
Intent stage: Shipped

Breaking change: No
Enterprise impact: None
Spec maturity: Incubation
Web Platform Tests: Yes

WPT details: https://wpt.fyi/results/service-workers/service-worker?label=master&label=experimental&aligned&q=service-workers%2Fservice-worker%2Ffetch-event-handled.https.html

Summary

A FetchEvent dispatched to a service worker is in a loading pipeline, which is performance sensitive. The new FetchEvent.handled property returns a promise that resolves when a response is returned from a service worker to its client. This enables a service worker to delay tasks that can only run after responses are complete.

Standards & signals

Specification: https://w3c.github.io/ServiceWorker/#fetch-event-handled
Firefox: Positive
Safari: Positive
Web developers: Positive
Tracking bug: https://bugs.chromium.org/p/chromium/issues/detail?id=1039558

Ecosystem

Web Platform Tests: https://wpt.fyi/results/?q=service-workers%2Fservice-worker%2Ffetch-event-handled.https.html
Chrome Platform Showcase: https://chrome-platform-showcase.paulkinlan-ea.deno.net/features
GenDN reference: https://gendn.paulkinlan-ea.deno.net/features
chrome.dev demos search: https://www.google.com/search?q=site%3Achrome.dev+FetchEvent.handled
MDN Web Docs: https://developer.mozilla.org/en-US/search?q=FetchEvent.handled
Baseline status: https://webstatus.dev/?q=FetchEvent.handled

Docs: https://github.com/w3c/ServiceWorker/issues/1397

Samples: https://github.com/w3c/ServiceWorker/issues/1397#issuecomment-479036562

Explainers: https://github.com/tingshao/FetchEvent.handled

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