Check your subtitles' reading speed
A caption can be perfectly timed to the audio and still fail: if it holds more text than a viewer can read before it disappears, they lose the words or the video. Check an existing file below for any cue that reads faster than a comfortable pace.
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What counts as too fast
Reading speed is measured in characters per second: the cue's character count, divided by how long it's on screen. This tool flags anything over 21 characters per second, just above the band most style guides use. Netflix's own guidelines cite 20 for adult content and 17 for children's, so 21 catches only what an average viewer would actually notice as rushed.
Whitespace and line breaks aren't counted as characters, since they're a layout choice, not something to read. Two cues with identical wording score the same whether the text is one line or wrapped across two.
Why this happens
- A cue built from a long, fast-spoken sentence with no natural break point
- Segmentation set to too many words per line for how quickly the speaker talks
- A translation that came out longer than the original language, without adjusting timing
The fix, in most cases, is splitting the cue rather than speeding it up: a shorter line held for the same duration reads at a lower rate. If you're editing in the main transcript editor, word-level timing means a split line gets real, individually-timed halves rather than an estimate.
This tool only checks. It doesn't change the file. Deciding whether to split a line, hold it longer, or shorten the wording is an editorial call, and it depends on things the timing alone can't tell you, like whether the video can spare the extra time on screen.
Frequently asked questions
Where does the 21 characters-per-second threshold come from?
It sits just above the commonly cited band for comfortable reading. Netflix's style guide uses 20 for adult programming and 17 for children's. 21 is a slightly looser ceiling so only clearly rushed cues get flagged.
Can this tool fix the cues it flags?
No, on purpose. Fixing a too-fast cue means either giving it more time (which the source video may not allow) or shortening the wording, and both are editorial decisions this tool can't make for you.
Does line-break formatting affect the score?
No. Whitespace is stripped before counting characters, so the same words score the same whether they're on one line or wrapped across two.
Does this check timing accuracy too?
No, only reading speed. For drift or offset problems, see the subtitle timing fixer instead.
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