Subtitle sync online: how to fix out-of-sync subtitles
Drop your subtitle file, then open the Sync tab. Before choosing a method, work out what kind of error you have: play the start of the video and note whether the subtitles are early or late, then jump to the end and check again. If the error is the same at both ends, it is a fixed offset and a shift will fix it. If it grows or shrinks over the film, it is a rate mismatch and needs a stretch or a two-point sync.
Whichever you use, load your video in the preview tab to check the result before you download. The video is played from your own disk and is never uploaded.
Fix a fixed delay with a shift
A fixed error usually means the video and the subtitles were cut from different versions: one has a studio logo or a longer intro that the other lacks. Enter the offset in seconds — positive to show subtitles later, negative to show them earlier — and every cue moves by that amount. Times that would fall below zero are held at zero, and the tool tells you how many were affected.
Fix drift with a frame-rate stretch
If the subtitles start in sync and slowly drift, the file was timed for a different frame rate. The classic case is film at 23.976 frames per second against a version sped up to 25 for PAL television: the video runs about 4.2% faster, so every time in the subtitles must be multiplied by the ratio between the two rates. The presets cover 23.976 to 25, 25 to 23.976, 29.97 to 30, 30 to 29.97, 24 to 25 and 25 to 24, and you can enter any ratio yourself.
You can find a ratio from any two matching points: divide the time between two dialogue lines in the video by the time between the same two lines in the file.
Two-point sync: fix offset and drift at once
Two-point sync is the most useful method when you do not know what is wrong. Play the video, note the true time at which the first line is spoken and the true time of the last, and enter both. The tool solves for the stretch and the offset that map the file’s first and last cue onto those times, and applies the same correction to every cue in between. It shows you the values it derived.
Worked example: the first line is spoken at 00:01:12 but the file shows it at 00:01:05, and the last line is spoken at 01:35:20 while the file shows it at 01:31:50. The tool derives a scale of 1.03728 and an offset of 4.58 seconds, so every cue start is multiplied by 1.03728 and then moved by 4.58 seconds.
Why not just use your player’s subtitle delay?
Players such as VLC let you nudge the subtitle delay while playing, which is fine for a single sitting. But it changes only playback, it does not fix the file, and it cannot correct a drift that changes over the film. Fixing the file itself means it plays correctly on every device — a TV, a phone, a media server — without adjusting anything.
Other checks this tool does for you
- Overlapping cues, and cues that end before they start, are reported, and fixed only when you click the button.
- Encoding is detected, so accented and non-Latin characters survive.
- You can edit the text or timing of any single cue in the table.
- Every change can be undone.
How to use it
- Drop your subtitle file onto the box.
- Check whether the error is a fixed delay or grows over time.
- Use Shift, Stretch or Two-point sync on the Sync tab.
- Check it against your video on the preview tab, then download.
Frequently asked questions
How do I fix subtitles that are out of sync?
Work out whether the error is constant or grows. A constant error is fixed with a shift by a number of seconds; a growing error needs a frame-rate stretch or a two-point sync using the true times of the first and last lines.
How do I sync subtitles that drift over time?
Use the frame-rate stretch if you know the two frame rates, or two-point sync if you do not: enter when the first and last lines really occur and the tool works out the correction.
What is the 23.976 to 25 fps problem?
Film is often 23.976 frames per second, but PAL video runs at 25. The video plays about 4.2% faster, so the subtitles have to be compressed by the same ratio to stay in step.
Can I preview the subtitles against my video?
Yes. Open the video preview, choose a video from your computer and the current subtitles are drawn over it. The video is played locally and is not uploaded.
Does it change my original file?
No. Your file is read in the browser and the corrected version is a new download. You can undo every change before downloading.
Is my subtitle file uploaded?
No. The file is read and converted in your browser and is never sent to a server. The site records only an anonymous count of the format pair and a rough size bucket, never the subtitle text.