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This registry defines the byte stream formats for use with the Media Source Extensions™ specification [ MEDIA-SOURCE ].
This registry is non-normative.
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 .
The working group maintains a list of all bug reports that the editors have not yet tried to address ; there may also be related open bugs in the GitHub repository of the Media Source Extensions™ specification.
This document was published by the Media Working Group as an Editor's Draft.
Publication as an Editor's Draft does not imply endorsement by W3C and its Members.
This is a draft document and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to cite this document as other than a work in progress.
This document was produced by a group operating under the W3C Patent Policy . W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent that the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy .
This document is governed by the 18 August 2025 W3C Process Document .
This
registry
is
intended
to
enhance
interoperability
among
implementations
and
users
of
SourceBuffer
objects
described
in
the
Media
Source
Extensions™
specification.
In
particular,
this
registry
provides
the
means
(1)
to
identify
and
avoid
MIME-type
collisions
among
byte
stream
formats,
and
(2)
to
disclose
information
about
byte
stream
formats
accepted
by
MSE
implementations
to
promote
interoperability.
The
registry
maintains
a
mapping
between
MIME-type/subtype
pairs
and
byte
stream
format
specifications.
The
byte
stream
format
specifications
describe
the
structure
and
semantics
of
byte
streams
accepted
by
SourceBuffer
objects
created
with
the
associated
MIME-type/subtype
pair.
This registry is not intended to include any information on whether a byte stream format is encumbered by intellectual property claims. Implementors and users are advised to seek appropriate legal counsel in this matter if they intend to implement or use a specific byte stream format.
To register an entry, file an issue in the Media Source Extensions Byte Stream Format Registry GitHub issue tracker so it can be discussed and evaluated for compliance before being added to the registry.
The Media Working Group may seek expertise from outside the Working Group as part of its evaluation, e.g., from the byte stream format specification editors or relevant standards group. If the byte stream format 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 Media Working Group reaches consensus to accept the candidate, send a pull request (either by editors or by the party requesting the candidate registration) that meets the following requirements:
[[generate
timestamps
flag]]
value
that
must
be
used
by
SourceBuffer
when
handling
the
byte
stream
format.
Once
consensus
to
accept
the
candidate,
a
pull
request
should
be
drafted
(either
by
editors
or
is
reached
by
the
party
requesting
the
candidate
registration)
to
register
Working
Group,
the
candidate.
The
registry
editors
will
review
and
merge
the
pull
request.
If a registration fails to satisfy a mandatory requirement specified above, then it may be removed from the registry (without prejudice). Existing entries cannot be deleted or deprecated otherwise.
Existing entries may be changed after being published through the same process as candidate entries. Possible changes include modification of the link to the publically available specification.
| MIME type/subtype | Public Specification(s) | Generate Timestamps Flag |
|---|---|---|
|
audio/webm
video/webm |
WebM Byte Stream Format [ MSE-BYTE-STREAM-FORMAT-WEBM ] | false |
|
audio/mp4
video/mp4 |
ISO BMFF Byte Stream Format [ MSE-BYTE-STREAM-FORMAT-ISOBMFF ] | false |
|
audio/mp2t
video/mp2t |
MPEG-2 TS Byte Stream Format [ MSE-BYTE-STREAM-FORMAT-MP2T ] | false |
|
audio/mpeg
audio/aac |
MPEG Audio Byte Stream Format [ MSE-BYTE-STREAM-FORMAT-MPEG-AUDIO ] | true |