Can people read your subtitles in time?
Drop an SRT or VTT. Every subtitle is checked for line length, number of lines, reading speed and overlaps — then shift the timing and save it in either format.
Runs in your browser. Nothing is uploaded, no signup.
For subtitles that come early or late. A time cannot go below zero.
0subtitles to fix
rules: 42 characters a line, 2 lines, 20 a second 1
Paste subtitles or drop an .srt / .vtt file. Each one is checked for line length, number of lines, reading speed and overlaps.
Watch an example
13 seconds · a made-up example
In the studio, captions are cut from the voice's own word timings.Join the beta
How it works
Short and checkable: every limit links to the platform's own page, read on 28 Oct 2026.
Checked against a published standard
Netflix's English timed text guide is one of the few public, precise ones: 42 characters per line, two lines at most, up to 20 characters a second for adults and 17 for children. Each subtitle gets its own verdict.
Reading speed is characters ÷ seconds
All the visible characters of a subtitle, spaces included and tags like <i> left out, divided by how long it stays on screen. Too fast, and people stop reading.
Shift and convert in one go
Slide every subtitle earlier or later by up to five seconds, then save as SRT (comma before the milliseconds, numbered) or WebVTT (point, WEBVTT header). Styling and positions are not kept.
What it doesn't do
- It doesn't fix the text for you: it says which subtitle breaks which rule.
- VTT styling, positions and notes are dropped when you save.
- The 42-character rule is written for film and series subtitles; for captions burned into a phone video, treat it as a ceiling.
- Your file is read and written in this tab only.
Questions
How many characters should a subtitle line have?
At most 42 characters a line and 2 lines, per Netflix's English timed-text guide.
How fast can subtitles be?
Up to 20 characters a second for adults and 17 for children (Netflix). Faster than that, people stop reading or miss the picture.
How do I shift subtitles that are out of sync?
Enter the offset in seconds (negative to show them earlier) and save the file again as SRT or VTT.
Sources
- 1Netflix Partner Help — English (USA) Timed Text Style Guide: 42 characters a line, 2 lines, 20 characters a second17 a second for children; change log 19 Dec 2025 · read 28 Oct 2026
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Captions timed to the word.
Vertiscale places every caption on the voice's own word timings, in whole phrases — on every version for every account.