Subtitle Sync & Repair
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Adjust an SRT or WebVTT file when subtitles arrive too early, too late or gradually drift. Review cue text and timing before exporting.
Preparing your tool…
A visual example
Move a subtitle without changing its duration
If every subtitle appears half a second too early, a constant +500 ms shift moves them later.
- Original cue
Start: 00:00:01,250
End: 00:00:03,250
You are here.
Before the shift
This cue starts at 1.250 seconds and ends at 3.250 seconds. Its duration is 2 seconds.
- Shifted cue
Start: 00:00:01,750
End: 00:00:03,750
You are here.
After a +500 ms shift
Both timestamps move by the same amount. The text and two-second duration remain unchanged.
A constant offset fixes a constant delay; it does not fix a delay that grows over time.
Illustrative example. Check the timing against the actual video. Existing overlaps and other reported cue problems still need review; the tool does not listen to the soundtrack to find the correct offset.
How to use it
- Read an SRT/WebVTT file or paste its source text, choosing the encoding when needed.
- Edit cue text/times and apply a millisecond shift or two synchronization anchors.
- Review overlaps, invalid durations and any format-specific conversion losses.
- Export SRT or WebVTT after resolving blocking errors.
The sample begins at 00:00:01,250. A +500 ms shift moves that cue to 00:00:01,750 while preserving its text and duration; its intentional overlap remains available for review.
Details & limits
SRT and WebVTT. Timing changes preserve cue order. Negative or reversed timestamps must be corrected before export.
When should I use two synchronization anchors?
Use two anchors when subtitles drift progressively out of sync, rather than having one constant delay. The tool maps the two source times to their chosen target times and adjusts the times between them. It does not listen to audio or discover those anchors automatically.
Choose a timing correction that matches the mismatch
Watch a recognizable spoken moment near the start and another near the end in your player. Compare both with the subtitle timestamps. A constant delay and a delay that grows through the video need different corrections; changing the subtitle format alone fixes neither.
Every subtitle arrives equally late
If the text appears 0.75 seconds late throughout, shift it by -750 ms. A cue from 00:00:03,000 to 00:00:05,000 becomes 00:00:02,250 to 00:00:04,250: the two-second duration stays the same. Use a positive shift when the subtitles appear too early. Check the earliest cue, since shifting backwards can create a negative start time.
The beginning matches but the end drifts
Use two reliable synchronization points spread across the recording. For example, mapping source 1 second to target 1.5 seconds and source 11 seconds to target 12.5 seconds moves a source time of 6 seconds to 7 seconds. This changes the timing scale, including cue durations, and continues beyond the two anchors. Review material before and after them too.
Check your result
- Replay the beginning, middle and end with the exported subtitle file, using the intended video version.
- Review negative times, nonpositive durations and reading warnings; an overlap may be intentional, so inspect its context.
- When converting WebVTT to SRT, check whether losing positioning or renumbering named cues is acceptable for your player.
If something looks wrong
Some scenes fit and others suddenly do not
The subtitle and video may contain different edits. A global shift or linear drift correction cannot account for an inserted or missing scene. Obtain matching source versions or adjust the affected cues individually.
Changing timings does not make the video playable
This tool edits subtitle text files, not video codecs or audio tracks. Check the player's video support separately; it does not listen to the recording to discover synchronization points.