Your subtitle file looks fine — until the client's platform rejects it, or a viewer can't read a caption that flashes past in half a second.

Subtitle QA & Repair Kit is a pre-delivery checker for SRT and VTT files. Drop in your files and it flags the problems that get subtitles rejected or make them hard to read:

- Invalid timecodes, end-before-start cues, overlapping cues

- Numbering gaps and out-of-order cues (SRT)

- Exact duplicate cues

- Reading speed (CPS) over your limit

- Lines longer than your limit, cues too short or too long

- Empty cues

One click applies the SAFE fixes — renumbering, sorting, removing exact duplicates, trimming stray whitespace — and converts between SRT and VTT. Everything else is flagged in a downloadable CSV report for your decision. Your caption text is never rewritten.

Runs 100% in your browser, offline. No uploads, no account, no subscription — your subtitle files never leave your machine.

What's in the ZIP

- index.html — the tool (open it in any modern browser, works offline)

- sample_broken.srt — a sample with 7 planted problem types so you can see exactly what the report looks like

- sample_clean.vtt — a clean file (expected: zero issues)

- README with usage and limits, plus the engine's automated test results (26 checks, all passing)

Who it's for

YouTube creators, course creators, freelance subtitlers and small video teams who deliver SRT/VTT files and want a fast final check before delivery.

Limits

A QA utility, not a subtitle editor: it doesn't create captions, translate, or re-time creatively. Thresholds (CPS 20, 42 chars/line, 0.8–7s) are adjustable defaults, not a broadcaster certification.