What Is a VTT File? The WebVTT Format, an Example, and What Browsers Actually Show
A VTT file ( .vtt , short for WebVTT, Web Video Text Tracks) is the subtitle format of web video. Like an SRT file, it's plain text: a list of cues, each with a start time, an end time and the words to show. On top of that it can carry positioning, styling and comments. It's the only subtitle format the HTML5 <track> element accepts, so any video player in a web page reads it. Most explanations…
A VTT file, or WebVTT, is the subtitle format used by web videos. It is a plain text file containing cues with start times, end times, and the text to display. VTT files can also include positioning, styling, and comments. HTML5 track element is the only player that accepts VTT files, so any web video player reads VTT files. Most explanations only mention styling and positioning, but this report tested which features actually display in Chrome and Safari.
The report wrote individual VTT files for each feature and tested them in Chrome 155 and Safari 26.2 on a Mac and iPhone. Five features were found to display correctly in both browsers: plain cue, NOTE block, cue identifier, hour-less timestamps, line:0, line:50%, position, align, size, vertical text, b, i, u, and classes. However, region and karaoke were not supported by either browser.
The report also tested 18 common ways to break VTT files and fed them to Chrome, Safari, ffmpeg, and a custom converter. Only four out of 17 test files broke in Chrome, while all five broke in Safari. Overlapping cues were shown correctly in Safari, but only the first cue was shown in Chrome after seeking. YouTube supports WebVTT but limits styling to b, i, and u.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
