Subtitle validator

If a caption file will not load or a player drops some lines, the cause is usually a formatting problem inside the file. This free subtitle validator parses your SRT or VTT and reports what is wrong: malformed timestamps, cues that end before they start, overlaps, and ordering issues, with the line where each problem occurs. It runs in your browser; your file is never uploaded.

Your file is processed entirely in your browser and never uploaded.

How to use it

  1. Paste your captions or drop your .srt or .vtt file below.
  2. The tool parses every cue and lists any problems it finds, marked as errors or warnings.
  3. Fix the flagged lines in your caption editor and re-check until it comes back clean.

A caption file FastScribe writes is well-formed to begin with: ordered cues, valid timestamps, nothing overlapping. Upload your video and download captions that load first time.

Get a caption file that validates →

Frequently asked questions

What is the difference between an error and a warning?

An error means the file is genuinely broken and a player may reject it or drop cues: a malformed timestamp, a cue that ends before it starts, an empty cue, or a missing WEBVTT header. A warning means the file will play but something looks off, such as two captions overlapping on screen or cues being out of order.

Are overlapping captions always wrong?

Not always: some styles intentionally hold one caption while another appears. That is why overlaps are flagged as warnings, not errors: the tool points them out so you can decide, rather than assuming they are mistakes.

Does a clean result guarantee my captions are correct?

It guarantees the file is well-formed: the timing and structure are valid. It cannot check whether the words are accurate or whether captions match the audio; that still needs a human eye or an accurate transcript to compare against.