Subtitle Duration Fixer
Fix subtitles that flash by too quickly, stay too long or overlap. The tool adjusts end times to your limits and never moves a start time, so the sync is kept.
- Automatic fix
- Sync preserved
- Standard presets
- Never uploaded
Drop subtitle files here
or
SRT · VTT · ASS / SSA · SBV · SUB · TTML · LRC · TXT
Your subtitles are processed on your device and are never uploaded.
How to fix subtitle duration
Three steps to display times that viewers can read.
- 1
Open your subtitles
Drop one or more subtitle files, pick them from your device or paste the text. Up to 100 files can be processed in one go.
- 2
Choose a preset or your own limits
Pick Netflix, BBC, TED, ARD/ZDF or YouTube, or set the minimum and maximum duration, target CPS and minimum gap yourself.
- 3
Review and download
The tiles show how many subtitles were extended, shortened and de-overlapped. Check the changed times in the preview and download the result.
What the subtitle duration fixer does
Six timing repairs that only touch end times.
Minimum duration
Extends subtitles that are shorter than the minimum, so short lines do not just flash on screen.
Maximum duration
Shortens subtitles that stay on screen longer than the maximum you set.
Readable speed
Extends subtitles that are too fast to read towards a target CPS, as far as the next subtitle allows.
Overlaps fixed
Ends a subtitle before the next one starts, so two subtitles are never shown at the same time.
Minimum gap
Keeps a gap between subtitles, such as 2 frames: 83 ms at 24 fps or 80 ms at 25 fps.
Start times untouched
Only end times are changed. Start times are never moved, so the subtitles stay in sync.
Standard presets
Apply the limits of Netflix, BBC, TED, ARD/ZDF or YouTube with one click, or use custom values.
Result at a glance
Tiles count extended, shortened and de-overlapped subtitles and those still outside the limits.
How long should a subtitle stay on screen?
A subtitle must stay visible long enough to be read, but not so long that it lingers after the speaker has finished. Subtitling standards put numbers on both ends. Netflix asks for a minimum duration of 5/6 of a second, which is 20 frames at 24 fps, and a maximum of 7 seconds. Between those limits, the reading speed decides: a subtitle with many characters needs more time than a single word.
Reading speed is measured in characters per second (CPS). Netflix allows up to 20 CPS for adult programmes and 17 for children, TED uses 21, the BBC works with about 17, and German public broadcasters with 15. To fix subtitle duration for a line that is too fast, the tool extends its end time towards the target CPS. It stops where the next subtitle begins, minus the minimum gap, because a start time is never moved.
Two more problems are repaired in the same run. Overlaps, where a subtitle is still on screen when the next one starts, are removed by ending the first one earlier. And a minimum gap of 2 frames is kept between consecutive subtitles, which is 83 ms at 24 fps and 80 ms at 25 fps, so the eye notices that the text has changed. Very small gaps left over between subtitles can be closed as well.
What the fixer changes, and the usual limits
| Problem | What the tool does | Typical limit |
|---|---|---|
| Subtitle is visible too briefly | Extends the end time to the minimum duration | 5/6 second (Netflix) |
| Subtitle stays on screen too long | Shortens it to the maximum duration | 7 seconds (Netflix) |
| Too much text for the time | Extends it towards the target CPS, as far as the next subtitle allows | 20 CPS (Netflix), about 17 (BBC), 15 (ARD/ZDF) |
| Two subtitles overlap | Ends the first one before the next one starts | No overlap |
| Subtitles follow each other without a pause | Keeps a minimum gap | 2 frames: 83 ms at 24 fps, 80 ms at 25 fps |
Tips
- Subtitles counted as still outside the limits have no room before the next subtitle. Shorten their text in the SRT Editor, since more time is not available.
- To see first how fast a file really is, analyse it in the Subtitle CPS Calculator, which shows the average, the fastest subtitle and a histogram.
- Run the SRT Validator afterwards with the same standard to confirm that durations, gaps and overlaps now pass.
- Duration fixing does not correct subtitles that are early or late. Shift them first with Subtitle Delay, then fix the durations.
Frequently asked questions
Can’t find your answer? Contact us — we reply quickly.
Will fixing durations put my subtitles out of sync?
No. Start times are never moved, so every subtitle still appears at the same moment as before. Only end times change.
What is a good minimum and maximum subtitle duration?
A widely used reference is Netflix: at least 5/6 of a second, which is 20 frames at 24 fps, and at most 7 seconds. You can apply these values with the preset or enter your own.
What does CPS mean?
CPS stands for characters per second and describes the reading speed a subtitle demands. Netflix allows 20 CPS for adults and 17 for children, TED 21, and German broadcasters 15.
Why are some subtitles still outside the limits?
Because there is no room: the next subtitle starts too soon for the current one to be extended. The tile shows how many are affected; shortening the text is the remaining fix.
What is the 2-frame gap?
It is a short pause between two consecutive subtitles so the viewer notices the change of text. Two frames are 83 ms at 24 fps and 80 ms at 25 fps.
Can I fix several files at once, and are they uploaded?
Up to 100 files can be fixed in one batch with the same settings. Everything runs in your browser, and the files are never uploaded.
More free subtitle tools
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