What Is a VTT File? WebVTT Format & How to Open .vtt Files

Key takeaways

• ●VTT = Web Video Text Tracks (WebVTT). A W3C-standardized plain-text subtitle file for HTML5 web video via the <track> element.
• ●File structure: WEBVTT header + cues. Line 1 must be the literal “WEBVTT”, then a blank line, then each cue: optional identifier, timecode (HH:MM:SS.mmm --> HH:MM:SS.mmm), caption text, blank line separator.
• ●Origin: W3C, drafted 2010. Designed as a modernization of SRT for browsers — adding a required header, styling support, cue positioning, and a formal specification SRT never had.
• ●Primary use: HTML5 web video. The only officially supported subtitle format in the HTML5 spec, plus Apple HLS streaming subtitle segments. Video.js, Plyr, Shaka Player all expect VTT.
• ●Open with any text editor. Notepad, TextEdit, VS Code all handle .vtt files. Subtitle Edit and Aegisub give proper sync editing.
• ●VTT vs SRT: period vs comma + WEBVTT header + styling. Trivial to convert either direction. Use VTT for HTML5 web video; use SRT for YouTube uploads, video editors, and universal delivery.

What does VTT stand for?

VTT stands for Web Video Text Tracks — the full format name is WebVTT. In writing, both “VTT file” and “WebVTT file” refer to the same thing; .vtt is the filename extension you save it as. The format was drafted by the W3C in 2010 as part of the HTML5 effort, evolving from an earlier WHATWG proposal originally called WebSRT (Web Subtitle Resource Tracks). It reached W3C Candidate Recommendation status and is now the format the HTML5 <track> element officially uses.

Source: W3C WebVTT: The Web Video Text Tracks Format (verified August 2026).

VTT file definition and meaning

A VTT file is a plain-text subtitle and caption file that stores captions and their timing information for web video. The file has a .vtt extension, must start with the literal string WEBVTT on its first line, and pairs each caption with a start and end timecode that tells the video player when to show it. Unlike SRT, VTT supports basic CSS-like styling, cue positioning, and metadata payloads — features that browsers need for accessible, responsive web video.

Multiple VTT files (one per language) work identically alongside a video — .vtt files in plural are the standard delivery format for multi-language HTML5 subtitle tracks (movie.en.vtt, movie.es.vtt, movie.fr.vtt), each attached via its own <track> element.

Beyond captions and subtitles, WebVTT also carries chapters (kind="chapters") and metadata payloads (kind="metadata") — a single file format serving multiple text-track roles in the HTML5 spec. If you have a plain SRT file and need a VTT, the conversion is two find-and-replace edits away.

WebVTT format and structure — .vtt anatomy

Every VTT file has this shape: a header line, a blank line, then one or more cues. Each cue has:

1. Optional cue identifier — any text on a line before the timecode arrow. Used to reference the cue from CSS or JavaScript. Skippable.
2. Timecode line — in the format HH:MM:SS.mmm --> HH:MM:SS.mmm. The period before milliseconds is the WebVTT rule (SRT uses a comma). Optional cue settings can follow (position, alignment, line, size).
3. Caption text — one or more lines of caption text. Supports inline styling tags (<i>, <b>, <c.className>).
4. Blank line — separates this cue from the next.

WEBVTT

1
00:00:00.000 --> 00:00:03.500
Welcome to the tutorial.

2
00:00:03.500 --> 00:00:07.200
Today we're looking at the
WebVTT subtitle file format.

3
00:00:07.200 --> 00:00:11.000 line:90%
The format is simple — the
quirks are where the file breaks.

The line:90% on cue 3 is a cue setting — it positions the caption at 90% down the video frame. WebVTT supports position, line, size, align, and vertical settings after the timecode. SRT has none of this. For the deep dive on subtitle formats generally, see what is an SRT file.

Origin — where WebVTT came from

WebVTT emerged from a specific problem: by 2010, HTML5 had introduced the <video> element, but there was no standard way to attach captions to browser-rendered video. The dominant subtitle format at the time — SRT — was widely used but never formally specified; each parser handled edge cases differently. Browsers needed a real spec.

The WHATWG initially proposed a format called WebSRT (Web Subtitle Resource Tracks) — essentially SRT with a required header and formal grammar. The proposal was refined by the W3C into WebVTT, renamed to reflect that the format serves multiple text-track roles beyond subtitles (captions, chapters, descriptions, metadata). The first public working draft appeared in 2010; the specification advanced through W3C Candidate Recommendation status over the following years.

Three things drove adoption. First, the HTML5 <track> element officially uses WebVTT — every browser vendor implemented it. Second, Apple adopted WebVTT for HLS streaming subtitle segments, giving it a major distribution role beyond the browser. Third, modern web video players (Video.js, Plyr, Shaka Player, hls.js) all expect VTT as their default subtitle format.

Today WebVTT is the web's answer to what SRT is for creator tools — the universal option in its context. Its parent, SRT, remains dominant everywhere else. Neither has replaced the other; they coexist because they optimize for different delivery paths.

What VTT files are used for

Six common workflows for VTT files in 2026:

VTT vs SRT vs ASS vs SCC vs TTML

WebVTT is one of several subtitle formats — each optimized for a different delivery context. Here's where each fits.

Practical rule of thumb: VTT for HTML5 web video; SRT for almost everything else. Use ASS for karaoke or precise styling control (anime fansubs). Use SCC or TTML/IMSC only if you're shipping to US broadcast or Netflix respectively. For the legal and accessibility framing around when captions are required, see captions vs subtitles.

How to open VTT files (viewers, editors, and text editors)

VTT files are plain text — any text editor opens them.

If double-clicking a VTT launches a media player, that's because the player is trying to load the file as a subtitle track. To edit the VTT text itself, right-click → Open With → choose a text editor.

How to create a VTT file

Three creation paths, ordered fastest to slowest:

Convert between VTT and SRT

Both directions are trivial — the formats are close cousins.

For a client-side conversion that runs in your browser (no upload), use our VTT to SRT converter — it reports honestly what got stripped in the process.

Common WebVTT quirks that trip people up

Four things that break VTT files in practice: