Subtitle Reading Speed Checker
A subtitle that's gone before it can be read is as bad as no subtitle. This checks the whole file against a reading speed, gives too-fast subtitles more time where there's silence after them, and lists the ones that need shorter text.
Runs in your browser. Your subtitles are never uploaded.
Check a file in three steps
Add the subtitles
Paste them or open the file.
Set the limits
17 characters per second and 1 second minimum are comfortable defaults; 20 is Netflix's limit for adult English.
Check, fix and download
See how many were too fast, and which ones still need shorter text.
What a good reading speed is
Reading speed is measured in characters per second (CPS): the subtitle's characters, spaces included, divided by how long it's on screen. Netflix's limit for English is 20 CPS for adult programmes and 17 CPS for children's programmes; many subtitlers and broadcasters work to 15 to 17 CPS for a comfortable read. 17 is the default here.
A subtitle that's too fast can be fixed two ways: keep it on screen longer, or say the same thing in fewer words. This tool does the first wherever the gap before the next subtitle allows, and leaves at least the gap you set between them. Subtitles with no room to grow are listed by number so you can shorten them.
The minimum time on screen catches flashes: Netflix asks for at least 5/6 of a second (about 0.83 s) per subtitle. Auto-generated subtitles often break this on short words like "Yeah."
What you get
Whole-file check
Every subtitle measured, not just one line at a time.
Automatic fixes
Fast subtitles stretched into the silence after them.
A to-do list
The subtitles that still need shorter text, by number.
Frequently
Asked Questions
What is CPS in subtitles?
Characters per second: how many characters a viewer has to read each second a subtitle is on screen. Lower is easier to read.
What's the Netflix reading speed limit?
For English, 20 characters per second for adult programmes and 17 for children's programmes.
Will it change the text?
No. It only makes subtitles last longer. Shortening the text is up to you; the tool tells you which ones need it.
Is my file uploaded?
No. It's checked in your browser.