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Subtitle Validator

Validate SRT and WebVTT subtitle files before delivery: timestamps, overlaps, line length and reading speed checked in batches of up to 20, with a JSON report. Runs entirely in your browser.

Validate before the platform does it for you

Every delivery pipeline eventually rejects a subtitle file — the only question is whether you hear about it from your own check or from a client's QC. The subtitle checker on this page validates SRT and WebVTT files the way a delivery spec would: timestamps parsed and ordered, overlaps flagged, lines measured against a character limit, and every cue tested against a maximum reading speed. Batches of up to 20 files are checked together and the findings can be downloaded as a JSON report to keep with the delivery.

Guidance, not certification

Validation here is a practical lint. Cue numbers refer to parsed order rather than custom cue IDs, markup is stripped before readability is measured, and WebVTT NOTE, STYLE and REGION blocks are ignored — so a clean report means 'ready for a human review', not 'specification-certified'. Fix findings in your editor, prioritising reversed or invalid timings, and re-export and re-run until the report is clean. WebVTT-specific checking is covered in depth on the VTT checker page, and if a validated file then needs a different format, the subtitle converter translates between SRT, VTT and ASS.

Local by design

Subtitles reveal scripts before release. Validating them in your own browser keeps that material off third-party servers entirely.

Frequently asked questions

What makes a subtitle file 'valid' here?

Every cue must have well-formed, forward-running timestamps; cues must not overlap unintentionally; lines must fit your character limit; and each cue must stay on screen long enough for its text to be read at your characters-per-second limit.

Which formats and how many files are supported?

SRT and WebVTT, up to 20 files per batch at 20 MB each and 80 MB combined. Files must be UTF-8; other encodings should be converted in your editor first.

Will the validator repair broken subtitles?

No. It reports findings — with cue numbers that refer to the parsed cue order — and your subtitle editor makes the fixes. Downloaded reports include failures, which makes them useful as delivery records.

Are overlaps always an error?

No. Overlapping cues can be deliberate, for example with two speakers. The validator flags them so a human reviews them in context instead of discovering them after publication.

Is anything uploaded during validation?

No. File reading, parsing and report generation all happen in this browser. Clear the batch or close the tab and everything is discarded.

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