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Timed Text Working Group


The Timed Text Working Group (TTWG) develops W3C Recommendations for online media captioning by developing and maintaining new versions and profiles of TTML (Timed Text Markup Language) and WebVTT (Web Video Text Tracks) based on implementation experience and interoperability feedback, and the creation of semantic mappings between those languages. The group also develops usage notes and manages registries to support implementors.

This is the Wiki for the activities associated with the updating of the Timed Text publications.

Key documents:

The TTWG operates under the Latest Operative W3C Process for all documents currently on the Recommendation Track.

TTML Pages


The group's publications are listed in detail on the Publications page.

Some important Documents

Document Status Publication Date
TTML1 (Second Edition) Recommendation 24 September 2013
TTML2 First Public Working Draft 12 February 2015
WebVTT First Public Working Draft 13 November 2014
IMSC1 Candidate Recommendation 19 May 2015
Mapping Between TTML and WebVTT Editor's Draft (Note) n/a
TTML Role Registry wiki n/a.

The TTML specification allows users to define and use roles for elements, in order to manage this across disparate organisations (without resorting to using complex namespaced prefixes) a set of roles is recorded in the TTML role registry page.

Timed Text Board Tracker for issues (summary from Github issues)

Timed Text Efforts and Specifications

Thanks to the Web and TV Interest Group, here's a list of Timed Text Efforts and Specifications.

TTWG Working Group F2F meetings

Working methods

The TTWG currently operates different working methods for development of TTML2 and IMSC than for WebVTT.

TTML2 and IMSC and other documents are generally discussed in weekly telephone conferences. Work on WebVTT tends to happen in github and on the reflector.

Those products that are managed with tracker are listed at products. Users of these products may identify issues within them, either before or after publication, and may wish to contribute developments, ideas or editorial changes to a product prior to publication.

Changes to products

All proposed changes must be recorded as issues which are managed on github following repos: imsc, ttml1, ttml2, ttml-webvtt-mapping and webvtt.


For bugs it is sufficient simply to raise an issue on github following repos: imsc, ttml1, ttml2, ttml-webvtt-mapping and webvtt.

New features

For development of new TTML features it is preferred that the features are described within #Change Proposals and discussed prior to approval either by teleconference meetings, usually held weekly, at face to face meetings, held on an occasional basis, or on the public email reflector which is archived here. The Chair approves change proposals according to the W3C consensus policy.


Where actions are assigned to members in order to progress an issue or a change proposal these are recorded in the tracker.

Mail archive

Emails to the group's public email address can be viewed in the public archive. Members can view emails to the group's member-only address in the member archive.

Change Proposals

As we look to creating the next version of the specification to address open issues we will adopt a lightweight change proposal mechanism. These change proposals are recorded in the Change Proposal Index


List of potential implementors call for participation [call-for-participation].

IMSC: You may report your implementation experience using our IMSC implementation Questionnaire.

Evidence of Wide Review

There is a page detailing WebVTT Wide Review

TTML Issues

Issues are tracked.

Issues that need further elaboration can be documented and discussed by adding a page link here.

  • Issue 151 Clarify syncbase in SMPTE continuous mode

TTML Documentation

You can help by providing Timed Text Documentation.


Please see the Efforts and Specifications page.