VTT MIME Type

About WebVTT subtitles files

The subtitle format for <track> in HTML video. Browsers ignore a track served with any other type, with no visible error. Files must start with WEBVTT; SubRip (.srt) subtitles look similar but use commas in timestamps and need converting first.

File signature

VTT files start with "WEBVTT" (after an optional BOM). The extension and the type a browser reports for an upload both come from the file name, so check these bytes on the server before trusting a file.

Serve .vtt with the right Content-Type

Content-Type: text/vtt; charset=utf-8

text/vtt vtt;

AddType text/vtt .vtt
AddCharset UTF-8 .vtt

@vtt path *.vtt
header @vtt Content-Type "text/vtt; charset=utf-8"

curl -sI https://example.com/file.vtt | grep -i '^content-type'
# Content-Type: text/vtt; charset=utf-8

Set the type in code

res.set('Content-Type', 'text/vtt; charset=utf-8');

import mimetypes

mimetypes.add_type('text/vtt', '.vtt')  # if your system doesn't know it
mimetypes.guess_type('file.vtt')[0]  # 'text/vtt'

mime.AddExtensionType(".vtt", "text/vtt; charset=utf-8")
w.Header().Set("Content-Type", "text/vtt; charset=utf-8")

Accept .vtt uploads

<input type="file" accept=".vtt,text/vtt">

The accept attribute only filters the file picker; users can still choose another file. Listing the extension as well as the type matters, because operating systems don’t always report the type you expect.

Related types

• .mp4 (video/mp4): MP4 video
• .webm (video/webm): WebM video
• .m3u8 (application/vnd.apple.mpegurl): HLS playlist

More web

.html , .css , .js , .mjs , .svg , .wasm , .webmanifest , .rss . Look up any extension or type with the MIME type lookup.

Sources

• IANA registration: text/vtt
• MDN: Common media types

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Frequently asked questions