Intent to Extend Experiment: Capability Elements <usermedia> MVP

[Chromestatus]

Contact emails

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

Explainer

https://github.com/w3c/mediacapture-extensions/blob/main/media-capture-elements-explainer.md

Specification

https://w3c.github.io/mediacapture-extensions/#media-capture-html-elements

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.

Reason this experiment is being extended

We are extending the origin trial for the Capability Element. Following the recent finalization of the specifications, this extension ensures that our key partners have sufficient time and stability to complete their adoption of the new implementation. Continuing this trial allows partners to maintain service in the legacy behavior mode of the usermedia element. This serves as a vital safety net, allowing them to finalize migration strategies and complete the necessary code updates to transition from the old behavior without risking service disruption.

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	151
Origin trial desktop first	144
Origin trial desktop last	148
Origin trial extension 1 end milestone	152
Origin trial extension 2 end milestone	155
DevTrial on desktop	144
Shipping on Android	151
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=6544047972941824

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 Extend Experiment 1: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/69f8fb56.050a0220.32fa05.04df.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.

[Alex Russell]

Hey folks,

Thank for requesting an extension. We discussed this intent at API OWNERS this morning, and it isn't entirely clear why we aren't sending an I2S instead. Do we not have clarity on the changes we want to make? Are the anticipated changes so fundamental that we can't imagine a true MVP subset that we could ship now while we discuss other options?

Best,

Alex

[Rick Byers]

In particular, I appreciate the (temporary) requirement "To ensure our partners currently using the Origin Trial do not experience unexpected service disruptions". But what if we decouple the question of extending the OT (for the "legacy API") from the question of just shipping the current API? Is there some reason the current API does not meet our bar for I2S? If we can ship it, I'd also be supportive of extending an OT to give your customers a bit more time (3 more months) to migrate to the shipped API.

Rick

--
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 blink-dev+...@chromium.org.
To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/f8d8322f-5742-4713-bfb4-cf83192adcf2n%40chromium.org.

[Thomas Nguyen]

Hi Alex and Rick,

Thanks for taking a look at this.

We actually shipped the version of <usermedia> that is closest to and aligned with the specifications. However, we are maintaining the current OT as a "reverse OT." This means that if a site keeps the OT token present, the <usermedia> element will retain its legacy behavior (more context on this approach here: https://groups.google.com/a/google.com/g/origin-trials-core/c/HXPxsWc1Ez4/m/7F77s0PRAwAJ)

Currently, we have two partners using <usermedia> who need more time to transition, so we would like to extend this "reverse OT" for the next 3 milestones.

--

Thomas Nguyen

Software Engineer

tun...@google.com

Google Germany GmbH

Erika-Mann-Straße 33

80636 München

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado

Registergericht und -nummer: Hamburg, HRB 86891

Sitz der Gesellschaft: Hamburg

Diese E-Mail ist vertraulich. Falls Sie diese fälschlicherweise erhalten haben sollten, leiten Sie diese bitte nicht an jemand anderes weiter, löschen Sie alle Kopien und Anhänge davon und lassen Sie mich bitte wissen, dass die E-Mail an die falsche Person gesendet wurde. 

     

This e-mail is confidential. If you received this communication by mistake, please don't forward it to anyone else, please erase all copies and attachments, and please let me know that it has gone to the wrong person.

[Rick Byers]

Ah, thank you - I'm sorry I forgot that it shipped already (should have known, explains why I was surprised to see an OT extension request).

Ok LGTM to extend the OT for 3 more milestones. But please ensure your partners know that further extension is unlikely to be approved.

Thanks!

   Rick