Find captions that move too quickly.
Measure every timed cue in characters per second and flag the lines that may be uncomfortable to read. Adjust the threshold for your audience and platform.
How this tool works
- 01
Choose the file format
Select SRT or VTT so the timing parser reads the timestamps correctly.
- 02
Set a reading-speed target
Start with 20 characters per second, then lower it for younger readers or dense material.
- 03
Review crowded cues
Rewrite, split, or extend any cue marked above your chosen threshold.
Practical guide
What to know before you download
What characters per second measures
Characters per second, or CPS, divides the number of visible characters in a cue by the time that cue remains on screen. A 40-character caption shown for two seconds measures 20 CPS. The checker treats repeated whitespace as one space and reports each cue separately, making it easier to find short, crowded captions hidden inside an otherwise readable file.
Use the threshold as a review filter
The default 20 CPS is a practical starting point, not a universal accessibility guarantee. Comfortable speed changes with language, audience age, reading ability, vocabulary, line breaks, and the complexity of the video. Lower the threshold when viewers need more reading time, then treat flagged cues as places for human review rather than automatic failures.
How to repair an overcrowded cue
First remove filler or rewrite the sentence without changing its meaning. If the words belong to separate phrases, split the cue at a natural pause. You can also extend its end time when there is clear space before the next caption. Avoid simply overlapping several cues, because the player may display them together or replace one before it can be read.
Reading speed is only one quality check
A cue can pass the CPS threshold and still be hard to read if it has awkward line breaks, too many lines, weak contrast, tiny text, poor placement, or inaccurate wording. Watch the full video with sound and without sound. This tool measures timing density; it cannot evaluate visual styling, speaker identification, sound-effect labels, or whether the transcription matches the audio.
Questions about this tool
What is a good caption reading speed?+
There is no single number that fits every audience and language. Use 20 characters per second as an initial review threshold, lower it for audiences who need more time, and always preview the actual captions in context.
Does the checker count words or characters?+
It counts visible characters after reducing repeated whitespace to a single space, then divides that count by the cue duration. The results therefore respond to both text length and how long the caption stays visible.
Does passing the check mean my captions are accessible?+
No. Reading speed is one useful signal. Accuracy, synchronization, contrast, size, position, line breaks, speaker labels, and meaningful audio descriptions or sound labels may also matter for the final experience.
Are my captions uploaded for analysis?+
No. The SRT or VTT text is parsed and measured in your browser. The checker does not require an account and does not send the pasted subtitle file to the product server.