LocalcraftTHE EVERYDAY TOOLKIT
LOCAL FILES. CLEAR RESULTS.

VTT Checker

Check WebVTT subtitle files for bad timestamps, overlaps, overlong lines and cues that flash past too fast to read. Batch-check up to 20 files and download a JSON report — all in your browser.

WebVTT files fail in quiet, specific ways

A VTT file can be technically present and practically broken: a cue that ends before it starts, two cues fighting for the same second, a line of 80 characters, a joke that disappears before anyone can read it. The subtitle checker above hunts exactly those faults across a batch of up to 20 VTT or SRT files, measuring each cue against limits you set — 42 characters per line and 20 characters per second by default — and produces a per-file list of findings plus a downloadable JSON report.

A checker, not a fixer — on purpose

The tool reports; your editor fixes. That separation matters, because only you know whether an overlap is a mistake or two speakers interrupting, and whether a fast cue is a problem or a single word. Work the findings in order: timing errors first, then line length, then reading speed, re-exporting and re-checking as you go. Note the practical limits of the check itself: markup is stripped for readability counts, and NOTE, STYLE and REGION blocks are ignored rather than validated, so this is a delivery lint, not a full WebVTT specification audit. When the file checks out but the format is wrong for your platform, the subtitle converter and its VTT to SRT page handle the translation.

Checked where the files live

Parsing and reporting run in your browser. Nothing about your subtitles is uploaded, stored or tracked.

Frequently asked questions

What does the VTT checker actually check?

It parses every cue and reports invalid or reversed timestamps, overlapping cues, lines longer than your limit, and cues whose text would need a faster reading speed than your characters-per-second limit allows. Findings are listed per file with cue numbers.

Does it check SRT files too?

Yes. The same checker accepts SRT and WebVTT batches, applying the same timing and readability rules to both. Export from your editor as UTF-8 .srt or .vtt and check them together.

Does checking change or fix my subtitles?

No. The checker reports problems; it never rewrites your files. Fix timing errors first in your subtitle editor, then long lines and fast cues, export again and re-check.

What do the line and speed limits mean?

Characters per line measures readability of each displayed line (42 is a common broadcast default); characters per second measures how fast a viewer must read during a cue (20 is a typical adult limit). Set both from the spec you are delivering to.

Are my subtitle files uploaded for checking?

No. Files are parsed in your browser and the report is generated locally. Unreleased episodes stay on your machine, and closing the tab discards the batch.

Related tools