A caption has to stay visible long enough to read while viewers follow the video. Characters per second is a useful diagnostic, but no single threshold proves a caption is accessible to every audience. Vocabulary, visual complexity and viewer needs matter too.
Use flags as a review queue
| Check | Our review flag | Next action |
|---|---|---|
| Reading speed | Above 20 visible characters per second | Allow more time or reduce wording without changing meaning |
| Line length | Above 42 characters in one line | Break the line at a phrase boundary |
| Cue timing | End before start or overlap | Review the affected cues against the audio |
| Line count | More than two lines | Reduce the block or split it at a useful point |
Free tools for this
Free to use, no account needed.
Run the checker
- Open the checker and paste or load the reviewed SRT or VTT captions.
- Check captions to see the flagged rows and their timestamps.
- Download the CSV if several people need to review the findings.
- Use the caption editor for specific corrections and rerun the checker on the exported file.
Check meaning as well as speed
Do not shorten a caption by removing a qualification that changes the claim. A slower cue with the wrong number is still wrong. Review names, figures and non-speech information that viewers need to understand the recording.
Play the captions at the size and frame shape your audience will use. Text that looks comfortable on a large desktop may crowd a phone frame. The automatic checks are a starting point for review, not a standards-compliance certificate.
Sources and further reading
Want captions without the cleanup?
Studio captions every word you said, a few words at a time, and changes any line you ask about in plain words.
