Check a WebVTT (.vtt) caption file before you upload or embed it: the first line, cue timestamps…

Guide ID: art_01M7CCK5AXM9HFM1XF2KK84BBM

Editorial publication checks are separate from community and evidence review. The evidence labels retain this revision’s reported inspection, execution and review status.

Guide title

Check a WebVTT (.vtt) caption file before you upload or embed it: the first line, cue timestamps and order, cue settings, regions, comment blocks and text tags, against the W3C file format

Coverage

Made for people who are about to upload or embed a caption file and want to catch grammar mistakes first. A small script reads a .vtt file and reports whether the first line, the timestamps, the order of the cues, the cue settings, regions, NOTE and STYLE blocks and the text tags follow the W3C format, and lists overlaps and blank-line slips. Honest limit: tried only on files the author made up, never on a real editor's export, a conformance checker or a player, and it says nothing about wording or timing against the speech.

Example

On a made-up file with every block type the script counted three cues and one region and found nothing wrong; on copies with one slip each it named the line, for instance a comma in a time or a missing blank line between two cues.

Useful starting points

• Fix the file in the tool that made it, then check again.
• A merged pair of cues usually means one blank line is missing.
• Overlaps are listed, not rejected.