textvtt

TextVTT commonly refers to the WebVTT subtitle format, a plain‑text, time‑based system used to provide captions, subtitles, and other metadata tracks for video content. While “textvtt” is not an official distinct standard, it is often used to describe WebVTT files, which use the .vtt extension and the MIME type text/vtt.

A WebVTT file starts with the header WEBVTT on its own line, followed by optional notes and a blank line. Cues specify start and end times in hours, minutes, seconds, and milliseconds, using the format 00:00:01.000 --> 00:00:04.000. A cue may have an optional identifier line above the timing line, and one or more lines of caption text. The file remains a UTF-8 text document.

Cue settings control presentation, placed after the end time on the timing line, and may include alignment, line, position, and size. For example, a cue line can specify align:left and line:0% to influence where text appears on the screen. WebVTT also supports comments, notes, and metadata cues.

WebVTT is widely supported in modern web browsers via the HTML track element and by many video platforms for accessibility and localization. It is commonly created or converted with subtitle editors and conversion tools, facilitating workflows that move between WebVTT and other caption formats such as SRT. Usage emphasizes accessibility, searchability, and compatibility across devices and players, making WebVTT a standard choice for online video captions.