If you have uploaded a video to a website, an online course platform or a video player, you have probably been asked for a VTT file. WebVTT is the subtitle and caption format of the web, and it sits behind most of the captions you see in HTML5 video players. This guide explains what a VTT file is, how it differs from SRT and how to translate one without breaking the timing.
What Is a VTT File?
A VTT file (Web Video Text Tracks) is a plain text file that contains subtitles, captions, chapters or descriptions for a video, together with the time each line should appear. The format is defined by the W3C in the WebVTT specification and is loaded in web pages through the HTML <track> element.
Every VTT file starts with the line WEBVTT. After that comes a list of cues. Each cue has an optional identifier, a timing line such as 00:00:04.000 --> 00:00:07.500 and one or more lines of text.
VTT vs SRT: What Is the Difference?
| VTT (WebVTT) | SRT (SubRip) | |
|---|---|---|
| Header | Starts with WEBVTT |
No header |
| Time format | Period before milliseconds (00:00:04.000) | Comma before milliseconds (00:00:04,000) |
| Cue numbers | Optional identifiers | Sequential numbers required |
| Styling and position | Cue settings, CSS styling, voice tags | Very limited |
| Main use | HTML5 video, web players, LMS platforms | Desktop players, editing tools, social platforms |
The two formats are close enough that converting between them is usually straightforward: add or remove the header, swap the decimal separator and keep the cue order. If you work mostly with SRT, our guide to SRT file translation covers that format in detail.
What Can a VTT File Contain?
- Subtitles and captions: dialogue, sound descriptions and speaker labels.
- Cue settings: instructions such as
line,positionandalignthat control where text appears on screen. - Voice and class tags: markup like
<v Anna>for speakers, or<i>and<b>for emphasis. - Comments: lines starting with
NOTEthat are ignored by players. - Chapters and metadata: separate tracks for chapter titles or data used by the player.
How to Translate a VTT File
- Check the source first. Make sure the timing is correct and each cue holds a complete thought. Fixing problems in the source saves work in every language.
- Translate the text, not the code. Timestamps, cue settings, tags and the
WEBVTTheader must stay exactly as they are. Using a translation tool that protects them prevents broken files. - Respect reading speed. Subtitles must be readable in the time they are on screen. Many teams aim for around 15 to 17 characters per second and two lines per cue.
- Adapt, do not just translate. Shorten sentences where needed and keep names, product terms and on-screen text consistent with your glossary.
- Review with the video. Watch the translated captions in the player to catch timing, line breaks and meaning issues.
- Name files clearly. Use language codes, for example
course-intro.de.vtt, and set thesrclangattribute on the track element.
Common VTT Translation Mistakes
- Deleting the
WEBVTTheader, so the player refuses the file. - Changing the time separator from a period to a comma.
- Translating or removing voice tags and cue settings.
- Lines that are too long, which overflow on mobile screens.
- Machine-translated captions published without any review.
Translating Captions at Scale
One video is easy. A course library with hundreds of videos in eight languages is not. At that scale, you need translation memory so repeated phrases are reused, a term base for product and course terms, and AI pre-translation followed by human review. For the bigger picture of subtitles, dubbing and voice-over, see our guide to video localization.
How WordBeam Helps
WordBeam supports subtitle formats such as SRT and SCC in its CAT editor, so translators see only the text while timestamps stay protected. VTT files can be converted to SRT in seconds with free tools, translated in WordBeam with translation memory, glossary and AI engines such as DeepL, GPT and Claude, then converted back. QA checks flag missing tags and numbers before you publish.
Frequently Asked Questions
How do I open a VTT file?
Any text editor can open it. Most video players, including VLC and modern browsers, can also display VTT captions alongside the video.
Can I convert VTT to SRT?
Yes. Remove the WEBVTT header, add sequential numbers and change the period before milliseconds to a comma. Many free tools do this automatically.
Is VTT better than SRT?
For web video, yes, because it supports positioning and styling and is the native format of the HTML track element. For desktop editing and many social platforms, SRT is still more common.