Subtitle sync and shift tool

Subtitles early, late, or slowly sliding out of step? Shift every line by a fixed amount, or give two correct times and let the tool stretch the rest into place.

  • Shift by ± seconds
  • Two-point resync for drift
  • SRT · VTT · SBV · ASS

Find out which problem you have

Watch the first minute and the last few minutes. If the error is the same at both ends, it is an offset. If the subtitles are fine at the start but late (or early) by the end, it is drift.

Offset or drift? Move the sliders

The dashed line is perfect sync. A constant offset moves the whole line up or down: one shift fixes it. Drift tilts it, so the error grows through the video: you need two points to straighten it.

0 min60 minspoken

Error at the start: 2.0 s · after 10 min: 27.8 s · after 60 min: 156.8 s

How two-point sync works

Two correct points define a straight line. For each subtitle the tool maps its old time t to new = spoken₁ + (t − old₁) × k, where k = (spoken₂ − spoken₁) ÷ (old₂ − old₁). When k is 1.0427 or 0.9590, the file was made for 25 fps and you are watching a 23.976 fps version, or the other way round. Choose points far apart (a line near the start and one near the end) for the most accurate result.

If the sync jumps in the middle

A sudden jump halfway through usually means the video has a scene the subtitle release did not (a different cut, or an ad break removed). Split the job: sync the part before the jump, then open the result in the SRT editor and shift only the lines after it.

Questions people ask

How do I fix subtitles that are out of sync?

If every line is early or late by the same amount, shift them all by that amount. If they start in sync but get worse, use two-point sync: give the correct time for an early and a late line and everything in between is stretched to fit.

Subtitles are ahead of the audio: positive or negative shift?

If the text appears before the words are spoken, the subtitles are early: shift them later with a positive number. If the text appears after the words, use a negative number.

Why do my subtitles drift out of sync over time?

Almost always a frame-rate mismatch: subtitles timed for a 25 fps release played against a 23.976 fps video (or the reverse) drift by about 4%, roughly 2.5 seconds every minute. Two-point sync fixes it exactly.

Is my subtitle file uploaded?

No. The file is processed in your browser and the synced file is created on your device.