Intent to Extend Experiment: Extended lifetime shared workers

[Chromestatus]

Contact emails

dom...@chromium.org, yyana...@chromium.org

Explainer

https://gist.github.com/domenic/c5bd38339f33b49120ae11b3b4af5b9b#file-1-explainer-md

Specification

No information provided

Summary

This adds a new option, `extendedLifetime: true`, to the `SharedWorker` constructor. This requests that the shared worker be kept alive even after all current clients have unloaded. The primary use case is to allow pages to perform asynchronous work that requires JavaScript after a page unloads, without needing to rely on a service worker.

Blink component

Blink>Workers

Web Feature ID

shared-workers

TAG review

https://github.com/w3ctag/design-reviews/issues/1089

TAG review status

Pending

Origin Trial Name

Extended lifetime shared workers

Chromium Trial Name

SharedWorkerExtendedLifetime

Origin Trial documentation link

https://gist.github.com/domenic/c5bd38339f33b49120ae11b3b4af5b9b#file-1-explainer-md

WebFeature UseCounter name

kSharedWorkerExtendedLifetimeFeatureEnabled

Risks

Interoperability and Compatibility

We intend to specify that the lifetime timeout for these shared workers be extended in the same way as service workers. Because the exact timeout of service workers is left implementation-defined, it's possible that code using this new feature could be non-interoperable. However, this has so far not proved to be a major problem in practice for service workers.

Gecko: Positive (https://github.com/mozilla/standards-positions/issues/1227) Some unofficial tentative positive signals and engagement in the proposal issue.

WebKit: No signal (https://github.com/WebKit/standards-positions/issues/492) Some unofficial tentative negative signals in the proposal issue.

Web developers: Positive The problem of wanting to perform asynchronous work during unload is well-known, with the service worker workaround currently deployed, including by Google properties.

Other signals:

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

Goals for experimentation

No information provided

Reason this experiment is being extended

Developer participation in the Origin Trial has increased significantly, with most of the growth occurring since mid-September. As this momentum is recent, an extension is needed to allow developers sufficient time to conduct thorough experiments and to provide us with more comprehensive usage data and insights. To aid developers in their experimentation, we have also improved debuggability. The chrome://inspect/#workers page now indicates when a SharedWorker is using the extendedLifetime option. Separately, the standardization process is progressing well. The corresponding pull request to the WHATWG HTML specification (https://github.com/whatwg/html/pull/11600) is under review and has received positive signals, including an LGTM from Mozilla. Extending the trial will allow this real-world testing to continue while the specification solidifies.

Reason this experiment is being extended

A major partner is about to start a large-scale experiment. We believe that extending the trial to cover their experiment window is crucial, as it will provide us with essential performance metrics and stability data at scale. This extension will prevent any service disruption for the partner and ensure we have sufficient evidence to support the final launch.

Ongoing technical constraints

No information provided

Debuggability

The chrome://inspect/#workers page indicates when a SharedWorker is using the extendedLifetime option.

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

No
Shared workers are not yet supported on Android and Android WebView. However, we are concurrently working on enabling them there, and when we do, this feature will also be supported.

Is this feature fully tested by web-platform-tests?

Yes
https://wpt.fyi/results/workers/tentative/SharedWorker-extendedLifetime.html

Flag name on about://flags

No information provided

Finch feature name

SharedWorkerExtendedLifetime

Requires code in //chrome?

False

Tracking bug

https://issues.chromium.org/issues/400473072

Estimated milestones

Origin trial desktop first	139
Origin trial desktop last	142
Origin trial extension 1 end milestone	145
Origin trial extension 2 end milestone	148

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).

We are currently discussing some details in preparation for specification. The exact nature of how the lifetime extension works with regard to non-window clients, particularly, has only recently reached a tentative conclusion.

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5138641357373440?gate=6195414653075456

Links to previous Intent discussions

Intent to Experiment: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6862683f.170a0220.16d1bf.0122.GAE%40google.com
Intent to Extend Experiment 1: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/68de2b1f.050a0220.58465.05c2.GAE%40google.com

This intent message was generated by Chrome Platform Status.

[Yoshisato Yanagisawa]

Note that the spec has been discussed in the WHATUP at TPAC 2025, and got positive feedback.

Please see: https://www.w3.org/2025/11/11-whatwg-minutes.html

2026年1月21日(水) 12:22 Chromestatus <ad...@cr-status.appspotmail.com>:

[Alex Russell]

Hey Yoshisato-san,

Thanks for all the care you're taking with this feature. LGTM to extend the OT.

As discussed at this morning's API OWNERS call, I'd encourage you to send an Intent-to-Ship as soon as possible. This feature doesn't add any fundamentally new risks, and it sounds like you've already got feedback from some OT partners. Will this new large parntner answer fundamental design questions that are still left open? If no, I'd encourage you to file a gapless I2S as soon as possible, and certainly as soon as you have confidence from this latest partner about the open design questions.

Best,

Alex