CaptionKit subtitle tools
Subtitle Checker & SRT Validator
Find common subtitle quality problems and get a clear suggestion for every affected cue.
Paste SRT or WebVTT text, or edit detected blocks directly.
Validation results
Select an issue to locate its cue in the source.
Ready to check your subtitles
Add an SRT or VTT file, then run the check to see prioritized issues and suggested fixes.
What the validator checks
A practical quality pass, not just a format test
CaptionKit checks structure, timing and readability in one pass, then links every finding back to the affected cue.
File structure
Find missing cue numbers, invalid timelines and blank subtitle blocks.
Timing and overlap
Flag reversed time ranges, overlaps, and cues that are unusually short or long.
Reading comfort
Review line length, line count and reading speed for Latin and CJK captions.
Focused corrections
Jump to a cue, edit it in place, or merge and split captions without uploading the file.
Example
Problem subtitle
2 00:00:03,000 --> 00:00:02,000 A very late caption
Validation finding
Cue 1 · 00:00:03,000 Start time is not before end time. Set the end time after the start time.
How to use
- 1Upload an SRT or VTT file, paste subtitle text, or type it into the source editor.
- 2Review prioritized findings and select any issue to open its subtitle block.
- 3Edit, merge or split cues, recheck automatically, then download the report or edited subtitle.
Common subtitle validation problems
Invalid timelines, missing cue numbers, blank blocks, overlaps and unusually fast or long captions are common. The readability limits shown here are general recommendations, not universal publishing rules.
Frequently asked questions
What does the subtitle checker detect?
It checks SRT and WebVTT structure, numbering, timelines, overlaps, duration, line length, line count and approximate reading speed.
Does the checker fix and upload my subtitle?
Nothing is uploaded. You can edit, merge and split cues locally, then download the edited subtitle or a separate validation report.