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WebCodecs Codec Registry

WebCodecs Codec Registry

Editor’s Draft, 12 February 2026

More details about this document
This version: https://w3c.github.io/webcodecs/codec_registry.html Latest published version: https://www.w3.org/TR/webcodecs-codec-registry/ Feedback: GitHub Editors: Paul Adenot (Mozilla) Eugene Zemtsov (Google LLC) Former Editors: Bernard Aboba (Microsoft Corporation) Chris Cunningham (Google Inc.) Participate: Git Repository. File an issue. Version History: https://github.com/w3c/webcodecs/commits

Copyright © 2026 World Wide Web Consortium. W3C® liability, trademark and permissive document license rules apply.

Abstract

This registry is intended to enhance interoperability among implementations and users of [WEBCODECS]. In particular, this registry provides the means to identify and avoid collisions among codec strings and provides a mechanism to define codec-specific members of [WEBCODECS] codec configuration dictionaries.

This registry is not intended to include any information on whether a codec format is encumbered by intellectual property claims. Implementers and users are advised to seek appropriate legal counsel in this matter if they intend to implement or use a specific codec format. Implementers of WebCodecs are not required to support any particular codec nor registry entry.

This registry is non-normative.

Status of this document

This section describes the status of this document at the time of its publication. A list of current W3C publications and the latest revision of this technical report can be found in the W3C standards and drafts index.

Feedback and comments on this specification are welcome. GitHub Issues are preferred for discussion on this specification. Alternatively, you can send comments to the Media Working Group’s mailing-list, public-media-wg@w3.org (archives). This draft highlights some of the pending issues that are still to be discussed in the working group. No decision has been taken on the outcome of these issues including whether they are valid.

This document was published by the Media Working Group as an Editor’s Draft. The group does not expect this document to become a W3C Recommendation.

Publication as an Editor’s Draft does not imply endorsement by W3C and its Members.

The W3C Patent Policy does not carry any licensing requirements or commitments on this document.

This document is governed by the 18 August 2025 W3C Process Document.

Table of Contents

  1. 1 Organization
  2. 2 Registration Entry Requirements
  3. 3 Audio Codec Registry
  4. 4 Video Codec Registry
  5. 5 Privacy Considerations
  6. 6 Security Considerations
  7. Index
    1. Terms defined by this specification
    2. Terms defined by reference
  8. References
    1. Normative References
    2. Informative References

1. Organization

This registry maintains a mapping between codec strings and registration specifications as described below.

2. Registration Entry Requirements

To register an entry, file an issue in the WebCodecs GitHub issue tracker so it can be discussed and evaluated for compliance before being added to the registry.

The Media Working Group might seek expertise from outside the Working Group as part of its evaluation, e.g., from the codec specification editors or relevant standards group. If the codec specification is not publicly available, it must be made available to the Working Group for evaluation. For the entry to be included, there needs to be interest from at least one implementer in the Working Group. If the Working Group reaches consensus to accept the candidate entry, send a pull request (either by editors or by the party requesting the candidate registration) that meets the following requirements:

  1. A unique codec string, a common name string, and a link to the codec’s public registration specification.

  2. The codec string requirements are as follows:

    1. If the codec string contains a fixed prefix with variable suffix values, the suffix must be represented by an asterisk and the registration’s public specification must describe how to fully qualify the variable portion of the string.

    2. Otherwise, if the codec is recognized by multiple strings, a single preferred string should be listed and the registration’s specification must list the other allowed strings.

    3. Otherwise, the codec is identified by a simple fixed string.

  3. Each registration’s specification must include a sequence of sections describing:

    1. Recognized codec strings.

    2. EncodedAudioChunk or EncodedVideoChunk internal data.

    3. AudioDecoderConfig or VideoDecoderConfig description bytes.

    4. Expectations for EncodedAudioChunk or EncodedVideoChunk [[type]].

  4. Where applicable, a registration specification may include a section describing extensions to the dictionaries used in the configure(), decode() and encode() methods of the decoder and encoder interfaces (e.g., AudioDecoderConfig, VideoDecoderConfig, AudioEncoderConfig, VideoEncoderConfig, VideoEncoderEncodeOptions).

Once consensus is reached by the Working Group, the registry editors will review and merge the pull request.

Existing entries cannot be deleted or deprecated. They may be changed after being published through the same process as candidate entries. Possible changes include expansion of the codec string to better qualify the codec, adjustments to the codec name string, and modification of the link to the codec’s specification.

3. Audio Codec Registry

Codec string Common name Registration specification
flac Flac FLAC codec registration [WEBCODECS-FLAC-CODEC-REGISTRATION]
mp3 MP3 MP3 WebCodecs Registration [WEBCODECS-MP3-CODEC-REGISTRATION]
mp4a.* AAC AAC WebCodecs Registration [WEBCODECS-AAC-CODEC-REGISTRATION]
opus Opus Opus WebCodecs Registration [WEBCODECS-OPUS-CODEC-REGISTRATION]
vorbis Vorbis Vorbis WebCodecs Registration [WEBCODECS-VORBIS-CODEC-REGISTRATION]
ulaw u-law PCM u-law PCM WebCodecs Registration [WEBCODECS-ULAW-CODEC-REGISTRATION]
alaw A-law PCM A-law PCM WebCodecs Registration [WEBCODECS-ALAW-CODEC-REGISTRATION]
pcm-* Linear PCM Linear PCM WebCodecs Registration [WEBCODECS-PCM-CODEC-REGISTRATION]

4. Video Codec Registry

Codec string Common name Registration specification
av01.* AV1 AV1 codec registration [WEBCODECS-AV1-CODEC-REGISTRATION]
avc1.*, avc3.* AVC / H.264 AVC (H.264) WebCodecs Registration [WEBCODECS-AVC-CODEC-REGISTRATION]
hev1.*, hvc1.* HEVC / H.265 HEVC (H.265) WebCodecs Registration [WEBCODECS-HEVC-CODEC-REGISTRATION]
vp8 VP8 VP8 codec registration [WEBCODECS-VP8-CODEC-REGISTRATION]
vp09.* VP9 VP9 codec registration [WEBCODECS-VP9-CODEC-REGISTRATION]

5. Privacy Considerations

Please refer to the section Privacy Considerations in [WEBCODECS].

6. Security Considerations

Please refer to the section Security Considerations in [WEBCODECS].

Index

Terms defined by this specification

Terms defined by reference

References

Normative References

[WEBCODECS] Paul Adenot; Eugene Zemtsov. WebCodecs. URL: https://w3c.github.io/webcodecs/ [WEBIDL] Edgar Chen; Timothy Gu. Web IDL Standard. Living Standard. URL: https://webidl.spec.whatwg.org/

Informative References

[WEBCODECS-AAC-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. AAC WebCodecs Registration. URL: https://w3c.github.io/webcodecs/aac_codec_registration.html [WEBCODECS-ALAW-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. A-law PCM WebCodecs Registration. URL: https://w3c.github.io/webcodecs/alaw_codec_registration.html [WEBCODECS-AV1-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. AV1 WebCodecs Registration. URL: https://w3c.github.io/webcodecs/av1_codec_registration.html [WEBCODECS-AVC-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. AVC (H.264) WebCodecs Registration. URL: https://w3c.github.io/webcodecs/avc_codec_registration.html [WEBCODECS-FLAC-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. FLAC WebCodecs Registration. URL: https://w3c.github.io/webcodecs/flac_codec_registration.html [WEBCODECS-HEVC-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. HEVC (H.265) WebCodecs Registration. URL: https://w3c.github.io/webcodecs/hevc_codec_registration.html [WEBCODECS-MP3-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. MP3 WebCodecs Registration. URL: https://w3c.github.io/webcodecs/mp3_codec_registration.html [WEBCODECS-OPUS-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. Opus WebCodecs Registration. URL: https://w3c.github.io/webcodecs/opus_codec_registration.html [WEBCODECS-PCM-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. Linear PCM WebCodecs Registration. URL: https://w3c.github.io/webcodecs/pcm_codec_registration.html [WEBCODECS-ULAW-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. u-law PCM WebCodecs Registration. URL: https://w3c.github.io/webcodecs/ulaw_codec_registration.html [WEBCODECS-VORBIS-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. Vorbis WebCodecs Registration. URL: https://w3c.github.io/webcodecs/vorbis_codec_registration.html [WEBCODECS-VP8-CODEC-REGISTRATION] Paul Adenot; Bernard Aboba. VP8 WebCodecs Registration. URL: https://w3c.github.io/webcodecs/vp8_codec_registration.html [WEBCODECS-VP9-CODEC-REGISTRATION] Paul Adenot; Eugene Zemtsov. VP9 WebCodecs Registration. URL: https://w3c.github.io/webcodecs/vp9_codec_registration.html