Intent to Ship: WebGPU: `subgroup_id` feature

[Chromestatus]

Contact emails

jrp...@google.com

Explainer

https://github.com/gpuweb/gpuweb/blob/486577ae07e0fe3c433859499a1b558ee7c5275b/proposals/subgroup-id.md

Specification

https://www.w3.org/TR/WGSL/#language_extension-subgroup_id

Summary

Functionality added to the WebGPU spec after its first shipment in a browser. The `subgroup_id` and `num_subgroups` built-in values are now available when the subgroups extension is enabled.

Blink component

Blink>WebGPU

Web Feature ID

webgpu

Motivation

The `subgroup_id` and `num_subgroups` built-in values are now available when the subgroups extension is enabled. This improves the process of scheduling work across subgroups in WebGPU compute shaders.

Initial public proposal

https://github.com/gpuweb/gpuweb/pull/5416

TAG review

No information provided

TAG review status

Pending

Risks

Interoperability and Compatibility

This feature has been approved in W3C GPU for the Web WG meetings including participants from Safari and Firefox. Minutes from W3C meeting where the decision to accept the proposal was finalized: https://github.com/gpuweb/gpuweb/wiki/GPU-Web-2025%E2%80%9010%E2%80%9021-WGSL#subgroup-id-uniformity-of-subgroup-id-5368

Gecko: No signal (https://github.com/mozilla/standards-positions/issues/1205#issuecomment-3312534193)

WebKit: Closed Without a Position (https://github.com/WebKit/standards-positions/issues/294#issuecomment-1877411933)

Web developers: No signals

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?

None

Debuggability

None

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

Yes
All platforms will eventually have support. Will immediately be available on Android, Android WebView, ChromeOS, Mac, and Windows, since those platforms already support WebGPU. WebGPU will also start shipping on Linux in M144 on some devices, so this feature will become available when WebGPU does.

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

Yes
WebGPU/WGSL have a conformance test suite (https://github.com/gpuweb/cts) that is regularly pulled into Chromium and part of the testing of Dawn/Tint in Chromium. While the CTS can be embedded in WPT, the WebGPU team opted to keep it separate in Chromium testing to use a customized harness for robustness and performance. CTS coverage for the feature was added here: https://github.com/gpuweb/cts/pull/4487

Flag name on about://flags

Enable Unsafe WebGPU

Finch feature name

UnsafeWGSLFeatures

Rollout plan

Will ship enabled for all users

Requires code in //chrome?

False

Tracking bug

https://crbug.com/454654255

Estimated milestones

Shipping on desktop	144
Shipping on Android	144
Shipping on WebView	144

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/5072447137251328?gate=4692381941235712

This intent message was generated by Chrome Platform Status.

[Chris Harrelson]

LGTM1

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