Free tool
Caption checker
Find the captions viewers can't read in time, lines that run too long and captions that overlap, then fix what can be fixed in one click.
Updated 25 October 2026
Your file stays in your browser. Nothing is uploaded.
2. Check
Open a caption file to check its reading speed, line length, line count, timing and overlaps.
What it checks
- Reading speed: at most 17 characters a second.
- Line length: at most 42 characters a line.
- Lines: at most two per caption.
- Time on screen: between 1 and 7 seconds.
- Overlaps: no caption runs into the next.
These are the limits common in broadcast and streaming caption guidelines, and the ones CaptionMe's own captions follow. The fix re-wraps lines, ends overlaps and gives short captions more time where there's room, without changing a word. Captions that are simply too dense need splitting, which takes the audio.
Let CaptionMe do it for every upload
CaptionMe's captions are built to these limits from word-level timing, and its editor flags the words it wasn't sure of. See plans or how it works.
Questions
What reading speed is too fast?
Around 17 characters a second is the common limit for adult viewers; above it, people miss lines. Children's content usually aims lower.
Why 42 characters a line?
It's the long-standing limit in caption guidelines: two lines of 42 fit on a TV or phone screen at a readable size.
Does the fix change my words?
No. It only re-wraps lines and adjusts timing within the gaps between captions.
Is my file uploaded?
No. It's checked and fixed in your browser.
More for YouTube captions
- YouTube auto-captions, explained How YouTube's automatic captions are made, which languages get them, why some videos have none, and how to turn them on, edit or remove them.
- How to fix YouTube's auto-captions Why YouTube's automatic captions misspell names and jargon, how to correct them in YouTube Studio, and how to stop fixing every upload by hand.
- How to remove auto-generated captions on YouTube Unpublish or delete the "(auto-generated)" caption track in YouTube Studio, and put your own captions in its place.
- YouTube caption file formats: SRT, VTT, SBV and YTT Which caption files YouTube accepts, how SRT, WebVTT and SBV differ, and where styled YTT (srv3) stands.
- Caption file converter Convert SRT, VTT, SBV, ASS and YouTube timed text into each other, with styling for ASS and YTT. Free, in your browser.
- YouTube chapter and timestamp maker Check YouTube chapters against YouTube's rules and fix them in one click, or draft chapters from a caption file. Free, in your browser.
- Caption timing shifter Captions out of sync? Move them all earlier or later, or fix drift from another frame rate. SRT, VTT, SBV, ASS and YTT. Free, in your browser.
- Captions to transcript Turn SRT, VTT and other caption files into a clean transcript in paragraphs, with optional timestamps. Free, in your browser.
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