Browser-local subtitle utility
Free subtitle reading speed and line length checker
Paste an SRT or VTT file to find cues that read too fast or run past a comfortable line length. Set your own limits; the check runs in your browser.
Reading-speed report
No file checked yet.
Method and limits
Use the result as a measurement, not a promise.
- Paste the full subtitle file below.
- Set the maximum characters per second and maximum line length for your audience or platform.
- Run the check to list every cue that exceeds either limit.
- Open those cues in a subtitle editor to split, shorten, or extend them.
How the numbers are calculated
For each cue, the tool counts the visible characters, divides by the cue’s on-screen duration to get characters per second, and measures the longest line. Any cue above your chosen thresholds is listed with its number and timing so you can find it quickly in an editor.
The check ignores formatting tags and treats timing exactly as written in the file. It measures readability, not translation quality or accuracy, and it cannot see the video, so treat the thresholds as guidance for your specific audience.
Browser-local by design
The text entered into this tool is processed by JavaScript in your browser. The page does not send that text to the Voice Typing Aid contact endpoint. Optional page analytics, if you consent, measures page interactions rather than the contents of the text fields.
Frequently asked questions
What is a good subtitle reading speed?
Common guidance for adult audiences is around 15 to 17 characters per second, with many streaming style guides capping at about 20. A cue above that range may flash by before a viewer can read it. This tool lets you set the limit and lists every cue that exceeds it.
How long should a subtitle line be?
Most style guides keep each line to roughly 37 to 42 characters and each cue to two lines. Longer lines force smaller text or wrapping and are harder to read quickly. The default check flags lines longer than 42 characters.
Does the checker change my file?
No. It only reads the file in your browser and reports which cues read too fast or run too long. It does not edit, upload, or store your subtitles.
Why do fast cues matter?
Reading speed decides whether subtitles are usable. Cues that exceed a comfortable characters-per-second rate are a frequent accessibility problem, especially for viewers relying on captions, and are worth splitting or extending in a subtitle editor.