Shift subtitle timings — fix out-of-sync subtitles
Fix out-of-sync subtitles by shifting every timestamp by a fixed offset — or correct the progressive drift that comes from a frame-rate mismatch.
Runs entirely in your browser — nothing is uploaded.
Negative moves subtitles earlier, positive moves them later.
Use this when subtitles drift progressively rather than being uniformly out.
All processing happens in your browser. Your file is never uploaded.
A constant offset fixes subtitles that are uniformly early or late. If they start in sync and drift further out as the film goes on, that is a frame-rate mismatch — use the rate conversion instead, which rescales rather than offsets.
How to use
- Drop in the subtitle file. SRT, VTT, SBV or ASS. The format is detected automatically.
- Work out which problem you have. Uniformly early or late means a fixed offset. Getting worse over time means a frame-rate mismatch.
- Enter the offset or rate change. Negative moves subtitles earlier, positive later.
- Download the corrected file. Saved in the same format it came in.
Questions
How do I know how much to shift by?
Play the video, note when a line is actually spoken and when the subtitle appears, and take the difference. If the subtitle appears 2.5 seconds early, shift by +2.5.
My subtitles start fine but drift further out. What is wrong?
That is a frame-rate mismatch, not an offset — the subtitles were timed against a version of the film running at a different speed. Use the frame-rate conversion instead; it rescales all timings proportionally rather than sliding them.
What is the 23.976 vs 25 fps thing?
Film is 24 fps, sped up to 25 for PAL broadcast and slowed to 23.976 for NTSC. Subtitles timed for one run about 4% off against the other, which is imperceptible at the start and about two minutes out by the end of a feature.
What if a shift makes cues start before zero?
They are clamped to the beginning of the file, and the tool tells you how many were affected so you know some early lines may now overlap.