Subtitle checker
A subtitle checker for SRT, VTT, ASS and SBV files: drop a subtitle file to see what’s wrong with it, and download a repaired copy.
The conversion runs in your browser. Your file is not uploaded.
What the subtitle checker does
The subtitle checker reads a subtitle file and lists every problem a player or platform could trip over: overlapping captions, captions out of order, empty or zero-length captions, captions too brief to read, lines that are too long and reading speeds that are too fast. Timing and ordering problems are repaired automatically; wording is never changed.
What the subtitle checker checks
| Check | Why it matters | Fixed automatically |
|---|---|---|
| Overlapping captions | Two captions on screen at once; some platforms reject the file | Yes — the earlier one is trimmed |
| Captions out of order | Players expect captions sorted by start time | Yes — sorted |
| End before start, zero length | The caption never appears | Yes — given a readable duration |
| Empty captions | Blank flashes on screen | Yes — removed |
| Too brief to read | Under about five-sixths of a second on screen | Yes — extended where the next caption allows |
| More than 2 lines | Covers too much of the picture | Reported |
| Lines over 42 characters | May wrap or shrink in players | Reported |
| Over 20 characters a second | Faster than most people read | Reported |
The limits the subtitle checker uses
The limits follow widely used subtitle style guides: 42 characters a line and two lines per subtitle come from Netflix’s English timed-text guide, which also sets reading speed at 20 characters a second for adult programmes. Problems with wording — long lines and fast reading speed — are reported rather than changed, because fixing them means rewriting or re-splitting text, which should be your decision.
Subtitle checker FAQ
How do I check a subtitle file for errors?+
Drop the subtitle file on the subtitle checker and a list of problems appears, each with its caption number. Click “Download fixed file” for a copy with timing and ordering problems repaired.
Does the subtitle checker change the wording of captions?+
The subtitle checker never changes wording: automatic fixes only touch timing, order and empty captions. Long lines and fast reading speed are reported for you to decide.
Which subtitle formats can be checked?+
SRT, WebVTT, ASS/SSA and SBV subtitle files can be checked, and the repaired file is saved in the same format.
What line length and reading speed does the subtitle checker allow?+
The subtitle checker flags lines over 42 characters, captions with more than two lines, and reading speeds above 20 characters a second, following Netflix’s English timed-text style guide.
Why does a platform reject a subtitle file?+
Platforms most often reject subtitle files with overlapping captions, captions out of time order, or an end time before the start time. The subtitle checker finds and repairs all three.
Is the subtitle file uploaded for checking?+
The subtitle checker runs in your browser, so the subtitle file is read on your device and is not uploaded.
Need subtitles from a video?
SubtitlePop listens to your video and writes the captions for you, with word-level timing. Try the subtitle generator or make a file with the SRT generator. New to subtitle formats? Read what an SRT file is.
Subtitle time shift
Fix out-of-sync subtitles: shift every caption in an SRT, VTT, ASS or SBV file earlier or later by any number of seconds. Free subtitle sync, in your browser.
SRT to VTT
Free SRT to VTT converter: convert SRT subtitles to WebVTT for HTML5 video and web players in one step. Runs in your browser — the file is never uploaded.