Check a subtitle file for errors
Check an SRT, VTT, ASS or TTML file for overlaps, impossible durations, reading speed, long lines and empty cues. Nothing is changed or uploaded.
Before a subtitle file is delivered — to a client, a platform, a broadcaster, or just to a video you are about to publish — it is worth knowing what is wrong with it. This page reads the file and reports, in order, every cue that overlaps the next one, ends before it starts, sits on screen too briefly or too long, duplicates its neighbour, or breaks the reading-speed and line-length limits professional subtitling works to. It changes nothing and downloads nothing: the point is the list.
Worth knowing
- Nothing is edited and there is no file to download. Every other repair tool here answers "what should this become"; this one only answers "what is wrong with it".
- The thresholds are yours to set. The defaults — 21 characters per second, 42 characters a line, at most two lines, one second minimum — are the values most broadcast specifications land near, but a platform you deliver to may define its own.
- Every problem on a cue is listed, not only the first. A line that is too fast, too long and overlapping the next one shows up three times, because fixing one of those does not fix the others.
- It is not only for SRT: VTT, ASS, SBV, MicroDVD, TTML, SAMI, LRC, JSON and CSV files are all read and checked the same way, since the checks are about timing and text rather than about a container.
FAQ
What actually counts as an error in a subtitle file?
Two kinds of thing. Some are unambiguously broken — a cue that ends before it starts, an empty cue, two cues on screen at once. The rest are readability limits that depend on where you are delivering: reading speed, characters per line, and lines per cue.
How do I fix what this finds?
Timing problems — overlaps, durations, gaps — repair in one pass with the overlap fixer or the full repair tool. Anything that needs a human decision, such as a line that is too fast to read, means shortening the wording or moving a cue, which is what the cue editor is for.
Is a file with no findings guaranteed to be correct?
It is structurally sound and inside your limits, which is what can be checked mechanically. Whether the translation is right, the line breaks fall at sensible phrase boundaries, or a cue matches what is actually said on screen are all judgements no validator can make for you.