Subtitle Sync (SRT Shifter)

When subtitles appear too early or too late, the fix depends on how they are off. If every line is off by the same amount, shift them all. If they start in sync but drift further apart, the subtitles were made for a different frame rate — typically 23.976 fps film against a 25 fps European release — and the times must be scaled. If you only know two moments, two-point sync works out both the scale and the shift. This tool does all three for SRT, WebVTT, ASS/SSA, SAMI (SMI), YouTube SBV and LRC, and changes nothing but the times. It runs in your browser; nothing is uploaded.

How to use this tool

1. Choose subtitle files or paste the text.
2. Pick the fix: a shift (with an optional "from" time), a frame-rate change, or two-point sync.
3. Enter the amount, the two frame rates, or two subtitle times with the times they should have.
4. Copy the result or download the file; it keeps its name, format and encoding conventions.

Formula

new time = a × old time + b

A shift uses a = 1 and b = the amount. A frame-rate change uses a = subtitle rate ÷ video rate and b = 0. Two-point sync solves a = (new₂ − new₁) ÷ (old₂ − old₁) and b = new₁ − a × old₁. Subtitles that would end before 0:00 are removed; one that would start before 0:00 starts at 0:00. Times are written back in the file's own style: comma or full stop, with or without hours, centiseconds in ASS.

Example

In a film, a line at 0:01:00 in the subtitle file is spoken at 0:01:02, and a line at 1:30:00 is spoken at 1:30:06. Two-point sync gives a = (5406 − 62) ÷ (5400 − 60) = 5344 ÷ 5340 = 1.000749 and b = 62 − 60 × 1.000749 = 1.955 s, so a subtitle at 2:00 moves to 120 × 1.000749 + 1.955 = 2:02.045.