Subtitle checker
Find the captions viewers struggle with. The checker measures reading speed in characters per second, line length, number of lines and time on screen for every caption, and lists every caption that breaks a rule you set.
Your subtitle file
Drop subtitle files here
SRT, VTT, ASS, SBV, TTML, SUB, SMI, LRC and more · up to 100 files
Or paste subtitle text
Your file is read by this page in your browser. It is not uploaded anywhere.
Letters look wrong? Choose the language group the file was made for.
MicroDVD and Spruce STL files count video frames. Choose the frame rate of the video the subtitles belong to.
Your result
The preview shows the beginning of the file. The download contains everything.
How to use it
Open your subtitle file
Choose or drop one or more subtitle files, or paste the text of one. Nothing is uploaded.
Set the rules
Keep the common limits or enter the ones from your style guide. The report updates straight away.
Fix the listed captions
Read the list of problems with caption numbers and times, then copy or download the report.
What is checked
Characters per second, or CPS, is the number of characters in a caption divided by the seconds it stays on screen. Spaces and punctuation count; line breaks and formatting tags do not. A caption above the limit disappears before most viewers finish reading it.
Line length is the number of characters in the longest line of a caption. Lines per caption counts the lines on screen at once. Time on screen flags captions that flash by too quickly or stay long after the words were spoken. Overlaps are captions that are still on screen when the next one starts.
Choosing the limits
The starting values, 20 characters per second, 42 characters per line, 2 lines, and between 1 and 7 seconds on screen, are close to the limits many streaming services and broadcasters publish for adult viewers. Style guides differ by language, platform and audience: subtitles for children are usually slower, and languages such as Japanese or Chinese count characters very differently. Enter the numbers from the guide you work to.
What the checker does not do
The checker reports problems; it does not change the file. It cannot tell whether a translation is good, whether the timing matches the speech, or whether a line breaks at a natural point. Use the time shifter or the subtitle cleaner to fix timing and overlap problems.
Questions and answers
What is a good reading speed for subtitles?
Many guides allow up to about 17 to 20 characters per second for adult viewers and less for children. Use the limit from the style guide you work to.
How many characters should a subtitle line have?
42 characters per line is a common limit for languages written in Latin letters. Some guides use 37 or 39, and Japanese and Chinese use much shorter lines.
Does the checker change my file?
No. It only reports. Your file stays exactly as it was.
Can I check several files at once?
Yes. Open them together, choose a file in the list to see its report, or download all reports as a ZIP.