Timed Text Working Group
Delivering Captioning and Video Description for the Web



The mission of the Timed Text Working Group is to develop W3C Recommendations for media online captioning by developing and maintaining new versions of the Timed Text Markup Language (TTML) and WebVTT (Web Video Text Tracks) based on implementation experience and interoperability feedback, and the creation of semantic mappings between those languages.

Code of Ethics and Professional Conduct

The W3C Code of Ethics and Professional Conduct applies to all TTWG work.

Discussion lists

Technical discussion takes place on GitHub repository issues and pull requests and on the Working Group discussion list, public-tt@w3.org (archive). This is a public mailing list; to subscribe to the public-tt mailing list, please check the subscription procedure.

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Wiki and Timed Text Resources

The TTWG also maintains the Timed Text wiki which includes a list of the TTWG's publications and a list of known implementations, resources and specifications.


Meetings are held at 1600 UTC (winter time, where it applies) weekly on Thursdays, duration 1 hour. By exception 2 hour meetings may be scheduled, beginning at 1500 UTC. In summer time, meetings begin 1 hour earlier in UTC time.

Upcoming meetings are visible at the TTWG project dashboard.

Recent Activity and list of repositories

All of the TTWG's repositories can be found at Timed Text Working Group - Repositories page. Recent activity on the repositories where work is active at the moment can be found on the following repository links:

Group repositories

Recommendation Track specification repositories

Test repositories

Working Group Notes, registries etc

Suspended Recommendation Track specification repositories

How to join the group

This group operates under the W3C Patent Policy, which ensures that specifications published by the group can be implemented on a royalty-free (RF) basis. To record agreement from all participants with that W3C Patent Policy, joining the group involves completing several steps:

When you join, you will be added to public-tt, the publicly archived mailing-list for the group.