Subtitle Sync Online — Fix Subtitles That Are Out of Sync
Open the SRT or VTT file and tell the editor how it is off. Same delay everywhere: shift every line at once. Right at the start but later and later towards the end: give the correct time of one early and one late line, and everything between is stretched to match.
Sync subtitles
Files are processed in your browser and never uploaded
Which Kind of Out-of-Sync Is It?
Subtitles go out of sync in a few typical ways, and each needs a different fix. Play a line near the start and a line near the end before you change anything: how far off each one is tells you which row you are in.
| What you see | Likely cause | Fix in this editor |
|---|---|---|
| Every line is early or late by the same amount | The subtitles were timed for a release with a longer or shorter intro, or the video was trimmed at the start | Shift times → All lines |
| Right at the start, later and later towards the end | Frame-rate mismatch: subtitles made for a 25 fps release played on a 23.976 fps file, or the reverse | Sync by 2 points, or Frame rate 25 → 23.976 |
| Right until one scene, then off by a fixed amount | A scene or an ad break was cut from the middle of the video | Shift times → From a line onward |
| Lines flash, overlap or appear in the wrong order | Cues out of order or overlapping after hand edits | Check → Sort lines by time, Fix overlaps |
| One or two lines are off, the rest is fine | A typo in a timestamp | Type the right time, or drag the block on the timeline |
Drift adds up fast: subtitles made for 25 fps run about 4% faster than a 23.976 fps video, so on a two-hour film the last line is close to five minutes early. No single shift can fix that.
Before You Retime Anything
Three checks that save an evening of nudging lines one by one.
Check 1
Is it the right cut?
Subtitles for a director’s cut or a TV version contain scenes your video doesn’t have. Retiming can line up the rest, but lines for missing scenes will still appear over the wrong picture.
Check 2
Measure both ends
Write down how far off an early line and a late line are. The same offset at both ends means a simple shift; a bigger offset at the end means drift, and two-point sync is the fix.
Check 3
Pick clear anchor lines
Use short lines that start right as someone speaks — a name, a greeting, a one-word reply. Lines that begin over music or mid-sentence make the measurement fuzzy.
How to Sync Subtitles Online
Three steps, all in your browser.
Open the subtitles and the video
Drop the SRT or VTT on the editor, then add the video or audio so you can hear where lines start. Both stay on your device.
Choose the fix
The timing tools open on their own: Shift for a constant delay, Sync by 2 points for drift, Frame rate if you know both rates. Press “Use playhead” to take a time straight from the player.
Check and export
Play a few lines across the file, then export SRT or VTT. If the result is off, Ctrl/⌘+Z undoes the whole change.
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