SRT/Caption File Formatter & Validator
Check an SRT caption file for timing errors, overlaps, long lines and reading speed, then download it cleaned up, renumbered, shifted or converted to WebVTT.
About this tool
Captions only help if people can read them in time. The checker reads each caption's timing (accepting a comma or a dot before the milliseconds, and times without hours) and flags captions that end before they start, overlap the one before, appear for under a second or more than seven, run to more than two lines, have lines longer than your chosen limit, or need reading faster than your chosen speed. The BBC's subtitle guidelines suggest around 37 characters a line and a reading speed of about 160 to 180 words a minute, roughly 15 to 17 characters a second.
The output is renumbered from 1 with standard timestamps. You can also sort captions into time order, shift every time earlier or later to fix a sync problem, and convert to WebVTT, the format used by the HTML <track> element. Everything happens in your browser; files you open aren't uploaded.