WebVTT
file format
WebVTT (Web Video Text Tracks) is a World Wide Web Consortium (W3C) standard for displaying timed text in connection with the HTML5 <track> element.
The early drafts of its specification were written by the WHATWG in 2010 after discussions about what caption format should be supported by HTML5—the main options being the relatively mature, XML-based Timed Text Markup Language (TTML) or an entirely new but more lightweight standard based on the widely used SubRip format. The final decision was for the new standard, initially called WebSRT (Web Subtitle Resource Tracks). It shared the .srt file extension and was broadly based on the SubRip format, though not fully compatible with it.
The prospective format was later renamed WebVTT. In the January 13, 2011, version of the HTML5 Draft Report, the <track> element was introduced and the specification was updated to document WebVTT cue text rendering rules. The WebVTT specification is a W3C Candidate Recommendation, and the basic features are supported by all major browsers.
Main differences from SubRip
WebVTT's first line starts with WEBVTT after the optional UTF-8 byte order mark
There is space for optional header data between the first line and the first cue
Timecode fractional values are separated by a full stop instead of a comma
Timecode hours are optional
The frame numbering/identification preceding the timecode is optional
Comments identified by the word NOTE can be added
Metadata information can be added in a JSON-style format
Chapter information can be optionally specified
Only supports extended characters as UTF-8
CSS in a separate file defined in the companion HTML document for C tags is used instead of the FONT element
Cue settings allow the customization of cue positioning on the video
Compatibility
Firefox implemented WebVTT in its nightly builds (Firefox 24), but initially it was not enabled by default. The feature had to be enabled in Firefox by going to the "about:config" page and setting the value of "media.webvtt.enabled" to true. YouTube began supporting WebVTT in April, 2013. As of July 24, 2014, Mozilla has enabled WebVTT on Firefox by default.
Begin with the source’s own compact description: “WebVTT” is file format. The dossier treats that line as a proposition to test through WebVTT, file and format, not as a finished interpretation.
Why this record matters
The phrase “file format” supplies a clear boundary for inquiry. It also exposes the unanswered questions: who defined that boundary, when it became stable and which sources sit outside it.
Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Jun 17, 2026. The linked authority identifier is Q3566973. 1 of 1 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank. The first chronological checks are 2010, 2011, 2013 and 2014.
Overview language is designed for orientation and should not be treated as a substitute for the evidence cited beneath it. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “WebVTT” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.