Media Working Group Charter

This charter has been replaced by a newer version.

The mission of the Media Working Group is to develop and improve client-side media processing and playback features on the Web.

Join the Media Working Group.

Start date 22 July 2021
End date 31 May 2023
Charter extension See Change History.
Chairs Chris Needham (BBC)
Jer Noble (Apple)
Team Contacts François Daoust (0.2 FTE)
Meeting Schedule Teleconferences: topic-specific calls may be held
Face-to-face: we will meet during the W3C's annual Technical Plenary week; additional face-to-face meetings may be scheduled by consent of the participants, usually no more than 3 per year.


Standardization efforts to develop media foundations for the Web, such as the HTMLMediaElement interface and Media Source Extensions, have helped turn the Web into a major platform for media streaming and media consumption. Building on the experience gained through implementation, deployment and usage of these technologies, and on incubation discussions within the Web Platform Incubator Community Group, the Media Working Group will extend media foundations with new standardized technologies to improve the overall media playback experience on the Web.

The scope of the Media Working Group is:

Out of Scope

The following features are out of scope, and will not be addressed by the Media Working Group:

  • The definition of any new codecs for audio and video
  • The definition of adaptive streaming mechanisms (but the group will develop mechanisms that enable/ease the implementation of such mechanisms within Web applications)


Draft state indicates the state of the deliverable at the time of the charter approval. Expected completion indicates when the deliverable is projected to become a Recommendation, or otherwise reach a stable state.

Normative Specifications

The Working Group will deliver the following W3C normative specifications:

Media Capabilities

This specification provides APIs to allow websites to make an optimal decision when picking media content for the user. The APIs expose information about the decoding and encoding capabilities for a given format but also output capabilities to find the best match based on the device’s display.

Draft state: Working Draft

Exclusion Draft: Media Capabilities, associated Call for Exclusion on 30-Jan-2020 ended on 28-Jun-2020. Produced under the previous Working Group Charter


This specification defines APIs to allow websites to create a floating video window always on top of other windows so that users may continue consuming media while they interact with other content sites or applications on their device.

Draft state: Working Draft

Exclusion Draft: Picture-in-Picture, associated Call for Exclusion on 30-Jan-2020 ended on 28-Jun-2020. Produced under the previous Working Group Charter

Media Session

This specification enables web developers to show customized media metadata on platform UI, customize available platform media controls, and access platform media keys such as hardware keys found on keyboards, headsets, remote controls, and software keys found in notification areas and on lock screens of mobile devices.

Draft state: Working Draft

Exclusion Draft: Media Session Standard, associated Call for Exclusion on 30-Jan-2020 ended on 28-Jun-2020. Produced under the previous Working Group Charter

Media Playback Quality

This specification extends media playback interfaces defined in HTML to add new features that can be used to detect the user perceived playback quality.

The group expects to work with the WHATWG to integrate the specification in the HTML specification, and does not plan to work on or publish the specification once integration in HTML has been completed.

Draft state: Editor's Draft

Autoplay Policy Detection

This new specification provides APIs to allow websites to determine the document-level autoplay policy and whether autoplay will succeed for a given media element in a page.

Draft state: Editor's Draft

Media Source Extensions

This specification extends the HTMLMediaElement interface defined in HTML to allow JavaScript to generate media streams for playback. The scope of this revision is the same as that of the W3C Recommendation published in November 2016, limited to the generation and control of media streams. This revision updates the W3C Recommendation to address maintenance issues against the specification and add the codec switching feature incubated in the Web Platform Incubator Community Group since then. Additional features that are strictly in the scope of this specification may be considered.

Draft state: Editor's Draft

Encrypted Media Extensions

This specification extends the HTMLMediaElement interface defined in HTML to control playback of encrypted content. This revision updates the W3C Recommendation published in September 2017 to address maintenance issues against the specification and add three minor features incubated in the Web Platform Incubator Community Group since then, namely: HDCP Detection, Encryption scheme capability detection and a means to avoid creating duplicate sessions within the same origin (building on alternatives to finding existing sessions). The inclusion of other features is considered out of scope for this group and would require rechartering.

Draft state: Editor's Draft


This specification defines interfaces for encoding and decoding of audio, video, and images.

Draft state: Working Draft

Exclusion Draft: WebCodecs, associated Call for Exclusion on 08-Apr-2021 will end on 05-Sep-2021. Produced under the previous Working Group Charter

Potential Normative Specifications

The following features have been identified as potential normative specifications and may be adopted as normative specifications by the Working Group if there is consensus in the group that they are ready to move to the Recommendation track:

Audio Focus API
An API to allow web applications to manage their audio focus, to improve the audio-mixing of websites with native apps so they can play on top of each other or play exclusively.
An API to support metadata event tracks, carried either in-band or out-of-band and synchronized to audio or video media, which are used to support use cases such as ad insertion or presentation of supplemental content alongside the audio or video. This includes the possible adoption of the Sourcing In-band Media Resource Tracks from Media Containers into HTML document to specify the handling of in-band events.
Stream format specifications and accompanying registries
Notes described in Other Deliverables define optional features for Media Source Extensions and Encrypted Media Extensions. The Working Group may move them to the Recommendation track.

The Working Group will not adopt these features until they have matured through the Web Platform Incubator Community Group or another similar incubation phase. If additional normative specifications need to be added to the Charter before the Charter expires, the Working Group will recharter with changes.

Other Deliverables

The Media Working Group will maintain non-normative stream format specifications for Media Source Extensions and Encrypted Media Extensions, develop new stream format specifications, and update corresponding registries. It will maintain the following Notes in particular:

To enhance interoperability among implementations and users of WebCodecs, the Media Working Group will also maintain a non-normative registry for the specification, and develop non-normative codec-specific registrations. This includes the following Working Drafts, intended to become Notes:

Other non-normative documents may be created such as:

  • Use case and requirement documents;
  • Test suite and implementation report for the specifications;
  • Primer or Best Practice documents to support web developers when designing applications.


Specification FPWD CR PR Rec
Media Capabilities Q1 2020 Q3 2021 Q2 2022 Q2 2022
Picture-in-Picture Q1 2020 Q3 2021 Q2 2022 Q2 2022
Media Session Q1 2020 Q3 2021 Q2 2022 Q2 2022
Autoplay Policy Detection Q4 2021 Q2 2022 Q1 2023 Q2 2023
Media Source Extensions Q2 2021 Q1 2022 Q4 2022 Q1 2023
Encrypted Media Extensions Q4 2021 Q3 2022 Q1 2023 Q2 2023
WebCodecs Q2 2021 Q2 2022 Q1 2023 Q2 2023

Note: The actual production of some of the deliverables may follow a different timeline. Schedule changes will be documented on the group home page.

Success Criteria

In order to advance to Proposed Recommendation, each specification is expected to have at least two independent implementations of each of feature defined in the specification.

Each specification should contain separate sections detailing all known security and privacy implications for implementers, Web authors, and end users, including analysis of fingerprinting surface introduced and suggested mitigation strategies, as applicable. For features that allow detection and/or negotiation of capabilities, the group will document architectural alternatives, particularly ones that minimize fingerprinting surface, and seek horizontal review as it makes its choice(s) among the alternatives. Where features are imported by reference to other specifications, analysis and mitigation of their privacy and security issues will be included in the referencing specification.

There should be testing plans for each specification, starting from the earliest drafts.

Each specification should contain a section on accessibility that describes the benefits and impacts, including ways specification features can be used to address them, and recommendations for maximising accessibility in implementations. The latest versions of the Media Accessibility User Requirements and Framework for Accessible Specification of Technologies (FAST) documents notably provide media related advice to ensure that specifications developed by the Working Group meet the needs of users with disabilities.

To promote interoperability, all changes made to specifications should have tests.


For all specifications, this Working Group will seek horizontal review for accessibility, internationalization, performance, privacy, and security with the relevant Working and Interest Groups, and with the TAG. Invitation for review must be issued during each major standards-track document transition, including FPWD. The Working Group is encouraged to engage collaboratively with the horizontal review groups throughout development of each specification. The Working Group is advised to seek a review at least 3 months before first entering CR and is encouraged to proactively notify the horizontal review groups when major changes occur in a specification following a review.

Additional technical coordination with the following Groups will be made, per the W3C Process Document:

W3C Groups

Accessible Platform Architectures (APA) Working Group
The Media Working Group will coordinate with the APA Working Group to help ensure its deliverables support accessibility requirements, particularly with regard to interoperability with assistive technologies, and inclusion in the deliverables of guidance for implementing the group's deliverables in ways that support accessibility requirements. The Media Working Group will also review updates made to media related requirements in accessibility documents such as the Media Accessibility User Requirements and Framework for Accessible Specification of Technologies (FAST) documents.
Audio Working Group
The Audio Working Group develops a client-side API to synthesize, process and render audio streams directly in script.
CSS Working Group
The CSS Working Group develops and maintains CSS. This includes work on the CSS Object Model. The Media Working Group expects to coordinate with the CSS Working Group on the definition of the screen interface of the Media Capabilities deliverable.
GPU for the Web Working Group
The GPU for the Web Working Group develops interfaces between the Web Platform and modern 3D graphics and computation capabilities present on native system platforms, including processing of media streams for processing or rendering on the GPU.
Media and Entertainment Interest Group
The Media and Entertainment Interest Group discusses media-related technologies on the Web, and identifies possible use cases and requirements for Media Working Group deliverables. The Interest Group also maintains liaisons with external media organizations that develop or reference media technologies and that may want to bring specific requirements to the Media Working Group.
Second Screen Working Group
The Second Screen Working Group develops the Remote Playback API that extends the HTMLMediaElement interface to allow rendering of media on secondary devices. The Picture-in-Picture specification developed by the Media Working Group follows a similar design.
Timed Text Working Group
The Timed Text Working Group develops specifications for media online captioning.
WebTransport Working Group
The WebTransport Working Group develops APIs that enable data transfer between browsers and servers with support for multiple data flows, unidirectional data flows, out-of-order delivery, variable reliability and pluggable protocols. One of the use cases for these APIs is streaming of media, using WebCodecs for media encoding and decoding.
Web Real-Time Communications Working Group
The Web Real-Time Communications Working Group develops APIs to capture, encode, process, transfer, decode and render media.
Open UI Community Group
The group researches components and controls across the web and also looks to native paradigms to bring interoperability for design systems, frameworks and the web platform. The Open UI CG is looking at ways to enable style-able and extensible video/audio controls for features that the Working Group develops.

External Organizations

Web HyperText Working Group (WHATWG)
The WHATWG maintains the HTMLMediaElement interface that some of the Media Working Group deliverables extend.
External media groups
As noted above, through the Media and Entertainment Interest Group (or directly, when needed), the Media Working Group expects to liaise with external organizations that develop or reference media technologies (e.g. ATSC, CTA, HbbTV Consortium, IETF, IPTVF-J, ITU-T, MPEG, SMPTE). See the Media and Entertainment Interest Group charter for a list of candidate groups.


To be successful, this Working Group is expected to have 6 or more active participants for its duration, including representatives from the key implementors of this specification, and active Editors and Test Leads for each specification. The Chairs, specification Editors, and Test Leads are expected to contribute half of a working day per week towards the Working Group. There is no minimum requirement for other Participants.

The group encourages questions, comments and issues on its public mailing lists and document repositories, as described in Communication.

The group also welcomes non-Members to contribute technical submissions for consideration upon their agreement to the terms of the W3C Patent Policy.

Participants in the group are required (by the W3C Process) to follow the W3C Code of Ethics and Professional Conduct.


Technical discussions for this Working Group are conducted in public: the meeting minutes from teleconference and face-to-face meetings will be archived for public review, and technical discussions and issue tracking will be conducted in a manner that can be both read and written to by the general public. Working Drafts and Editor's Drafts of specifications will be developed on a public repository and may permit direct public contribution requests. The meetings themselves are not open to public participation, however.

Information about the group (including details about deliverables, issues, actions, status, participants, and meetings) will be available from the Media Working Group home page.

Most Media Working Group teleconferences will focus on discussion of particular specifications, and will be conducted on an as-needed basis.

This group primarily conducts its technical work on GitHub issues. The public is invited to review, discuss and contribute to this work.

The group may use a Member-confidential mailing list for administrative purposes and, at the discretion of the Chairs and members of the group, for member-only discussions in special cases when a participant requests such a discussion.

Decision Policy

This group will seek to make decisions through consensus and due process, per the W3C Process Document (section 3.3). Typically, an editor or other participant makes an initial proposal, which is then refined in discussion with members of the group and other reviewers, and consensus emerges with little formal voting being required.

However, if a decision is necessary for timely progress and consensus is not achieved after careful consideration of the range of views presented, the Chairs may call for a group vote and record a decision along with any objections.

To afford asynchronous decisions and organizational deliberation, any resolution (including publication decisions) taken in a face-to-face meeting or teleconference will be considered provisional. A call for consensus (CfC) will be issued for all resolutions (for example, via email, GitHub issue or web-based survey), with a response period from one week to 10 working days, depending on the chair's evaluation of the group consensus on the issue. If no objections are raised by the end of the response period, the resolution will be considered to have consensus as a resolution of the Working Group.

All decisions made by the group should be considered resolved unless and until new information becomes available or unless reopened at the discretion of the Chairs or the Director.

This charter is written in accordance with the W3C Process Document (Section 3.4, Votes) and includes no voting procedures beyond what the Process Document requires.

Patent Policy

This Working Group operates under the W3C Patent Policy (Version of 15 September 2020). To promote the widest adoption of Web standards, W3C seeks to issue Web specifications that can be implemented, according to this policy, on a Royalty-Free basis. For more information about disclosure obligations for this group, please see the W3C Patent Policy Implementation.


This Working Group will use the W3C Software and Document license for all its deliverables.

About this Charter

This charter has been created according to section 5.2 of the Process Document. In the event of a conflict between this document or the provisions of any charter and the W3C Process, the W3C Process shall take precedence.

Charter History

The following table lists details of all changes from the initial charter, per the W3C Process Document (section 5.2.3):

Charter Period Start Date End Date Changes
Initial Charter 22 May 2019 31 May 2021 none
Chair update 29 April 2021
  • Mounir Lamouri steps down as co-Chair
  • Chris Needham appointed co-Chair
Extended 19 May 2021 30 June 2021 End date adjusted
Rechartered 22 July 2021 31 May 2023
  • Adjusted boilerplate text to match latest charter template
  • Added WebCodecs to the list of deliverables
  • Dropped Persistent usage record sessions feature from EME description
  • Updated milestones and coordination list