TTML

TTML, or Timed Text Markup Language, is an XML-based markup language for encoding timed text tracks used with video and audio-visual content. It is designed to represent captions, subtitles, and other forms of timed text and to provide timing, styling, and layout information that can be consumed by media players.

A TTML document typically consists of a root element, a head with styling and layout specifications, and a body containing a hierarchy of div and p elements. Each caption block (p) includes timing attributes such as begin and end, and may reference a region for placement and a style for appearance. Regions define screen position and size; styling definitions specify font properties, color, alignment, and line breaks. TTML supports multiple languages and can include inline markup for spans with different styling.

Profiles and deployment: The standard defines profiles such as the distribution format exchange profile (DFXP/TTML) that are used in broadcast and on-demand services. TTML tracks are carried in various container formats and streaming protocols, including MPEG-DASH and adaptive streaming environments, and are used by broadcasters and streaming platforms to deliver accessible captions and subtitles.

Relation to other formats: TTML is one of several approaches to timed text; WebVTT is another widely adopted web-friendly format. TTML provides richer styling and layout capabilities through its XML schema, making it suitable for more complex captioning and multilingual subtitling use cases, especially in broadcast and streaming workflows.

Standards and governance: TTML was published by the World Wide Web Consortium (W3C) as a recommendation with subsequent revisions. It has also been incorporated into international broadcasting standards and profiles that promote interoperability across devices and platforms.