Intent to Extend Experiment: Capability Elements <usermedia> MVP

[Chromestatus]

Contact emails

lemi...@google.com, tun...@google.com

Explainer

https://github.com/WICG/PEPC/blob/main/usermedia_element.md

Specification

https://github.com/w3c/mediacapture-extensions/pull/168

Summary

Usermedia Capability Element, is a declarative, user-activated control for accessing the starting and interacting with media streams. This addresses the long-standing problem of permission prompts being triggered directly from JavaScript without a strong signal of user intent. By embedding a browser-controlled element in the page, the user's click provides a clear, intentional signal. This enables a much better prompt UX and, crucially, provides a simple recovery path for users who have previously denied the permission. Note: This feature was previously developed and tested in an Origin Trial as the more generic <permission> element. Based on feedback from developers and other browser vendors, it has evolved into capability-specific elements to provide a more tailored and powerful developer experience.

Blink component

Public Trackers > Chromium Public Trackers > Chromium > Internals > Permissions > PermissionElement

Web Feature ID

permissions

TAG review

https://github.com/w3ctag/design-reviews/issues/1218

TAG review status

Issues addressed

Origin Trial Name

UserMediaElement

Goals for experimentation

This Origin Trial serves two primary purposes: ensuring continuity for existing partners who have successfully integrated this pattern, and providing a platform to validate and iterate on the new, capability-specific <usermedia> element. While our previous Origin Trial for <permission> provided strong evidence for the core user-initiated model, feedback from developers and browser vendors prompted us to evolve the design. This new trial is essential for gathering insights on a refined, data-centric API shape to help us reach cross-browser consensus. To ensure a seamless transition and prevent disruption for our valued OT partners, this trial will initially launch with an API shape that is functionally equivalent to the previous <permission> trial, simply using the new <usermedia> element name. This provides a stable foundation from which we will iterate based on further discussion. Our goal is to evolve this element towards our proposed data-centric design (https://github.com/WICG/PEPC/blob/main/usermedia_element.md). However, we recognize that this more advanced API has raised compatibility and complexity concerns with developers (https://github.com/WICG/PEPC/issues/62). Therefore, a primary objective of this trial is to work closely with the community to address these concerns and refine the final API. TPAC WebRTC minutes https://www.w3.org/2025/11/11-webrtc-minutes.html#551

Chromium Trial Name

UserMediaElement

Origin Trial documentation link

https://github.com/WICG/PEPC/blob/main/usermedia_element.md

WebFeature UseCounter name

kHTMLPermissionElement

Risks

Interoperability and Compatibility

There is a risk that this feature fails to be adopted by other browsers. This can be mitigated by backwards designing a reasonable fallback mechanism so that the element can degrade gracefully if the it's in an unsupported environment.

Gecko: Under consideration (https://github.com/mozilla/standards-positions/issues/1392)

WebKit: No signal

Web developers: Positive https://github.com/WICG/PEPC/issues/2#issuecomment-2393820279 https://github.com/WICG/PEPC/issues/2#issuecomment-2393861768 https://github.com/WICG/PEPC/issues/2#issuecomment-2393911331 https://github.com/WICG/PEPC/issues/2#issuecomment-2619657041 https://github.com/WICG/PEPC/issues/62#issuecomment-3482975001 https://github.com/WICG/PEPC/issues/62#issuecomment-3482981942 https://github.com/WICG/PEPC/issues/62#issuecomment-3498355775 https://github.com/WICG/PEPC/issues/62#issuecomment-3513734884

Other signals:

Ergonomics

No foreseen ergonomics risks.

Activation

A polyfill can help developers use this feature without risking broken functionality on non-supporting browsers.

Security

https://github.com/WICG/PEPC/blob/main/explainer.md#Security

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?

Feature is not shipping on WebView due to it requiring permission manager embedder support.

Reason this experiment is being extended

We are looking to collect more feedback on the updated <usermedia> element API design. Based on feedback from https://github.com/w3c/mediacapture-extensions/pull/168/, we anticipate some changes to the API. As a result, we have decided not to launch this feature in M149. To ensure our partners currently using the Origin Trial do not experience unexpected service disruptions, we will need to extend the OT.

Ongoing technical constraints

No information provided

Debuggability

The element raises issues to the devtools issues panel which help developers debug issues with their usage of the element.

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

No
The element is not supported on Android WebView as it requires permission manager support to function and the WebView permission manager defers most permission decisions to the embedder by design.

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

Yes
https://wpt.fyi/results/html/semantics/permission-element/usermedia

DevTrial instructions

https://github.com/WICG/PEPC/blob/main/HOWTO.md#enabling-usermedia

Flag name on about://flags

No information provided

Finch feature name

UserMediaElement

Requires code in //chrome?

True

Tracking bug

https://crbug.com/443013457

Availability expectation

Feature is available only in Chromium browsers. We are not aware of other browsers adoption.

Adoption expectation

Feature is used by specific partner(s) to provide functionality within 12 months of launch in Chrome. Partners who are tested the feature in OT are expected to continue usage.

Adoption plan

We are planning to publish on developer.chrome.com and do further partner outreach

Non-OSS dependencies

Does the feature depend on any code or APIs outside the Chromium open source repository and its open-source dependencies to function?

No

Estimated milestones

Shipping on desktop	150
Origin trial desktop first	144
Origin trial desktop last	148
Origin trial extension 1 end milestone	152
DevTrial on desktop	144
Shipping on Android	150
Origin trial Android first	144
Origin trial Android last	148
DevTrial on Android	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).

This is an MVP launch. The MVP feature is fully functional and used by developers right now. We are working closely with the WebRTC on post-MVP features, the open topics will based on the foundation of the MVP, that we agreed upon with the WebRTC. Some of the open topics are for example: In the future, we might want to add a parameter to the getUserMedia algorithm so that the algorithm can determine whether the getUserMedia is called from the <usermedia> element or getUserMedia API. Potential to add additional attributes for <usermedia> interface. We're putting finishing touches on the spec now, work-in-progress PR is here, but once that lands we want to ship for M149 so wanted to start the discussion now.

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/4926233538330624?gate=5103061887483904

Links to previous Intent discussions

Intent to Prototype: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/692719de.050a0220.17ec37.00c3.GAE%40google.com
Intent to Experiment: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6942ed09.050a0220.1050d6.0961.GAE%40google.com
Intent to Ship: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/69dfa184.050a0220.c8e20.03e8.GAE%40google.com

This intent message was generated by Chrome Platform Status.

[Rick Byers]

Continuing to iterate on the design given the recent feedback (despite approved I2S) sounds right to me. LGTM to OT for another 3 milestones. Thanks for taking the time to address the feedback and continue to iterate!

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