⏱️ Subtitle Shifter (Resync)
Captions running early or late? Shift every cue by a set number of seconds to resync, SRT or VTT, all locally.
Positive delays the subtitles, negative moves them earlier.
Everything runs locally in your browser, your subtitles are never uploaded.
How the subtitle shifter (resync) works
When subtitles are consistently ahead of or behind the audio, every cue needs moving by the same amount. Enter a shift in seconds, positive to delay the subtitles (they appear later), negative to move them earlier, and the tool converts each cue's start and end timestamp to milliseconds, adds the offset, and writes them back in the original format (SRT or VTT). Both the start and end move by the identical amount, so every caption keeps its original on-screen duration; only its position on the timeline changes. Times can't go below zero, so any cue that would be pushed before 00:00 is clamped to the start.
This fixes a constant offset, the whole track being a second or two out, not drift, where the gap grows over the film (a frame-rate mismatch, which needs stretching rather than shifting). Work out the offset from one known line: if a caption shows at 00:10 but should be at 00:12, shift by +2 seconds. It's pure text math done on your device.
Frequently asked questions
How do I resync subtitles that are out of sync?
Load the SRT or VTT, find how many seconds off one line is, and enter that as the shift, positive if the subtitles are early (to delay them), negative if late. Every cue moves by that amount; download the fixed file.
Does it work for both SRT and VTT?
Yes. It detects the format from the file and keeps it. SRT stays SRT (comma milliseconds, numbered), VTT stays VTT (WEBVTT header, dot milliseconds).
What if the subtitles drift more over time?
A constant shift only fixes a fixed offset. If the gap grows through the video, that's a frame-rate mismatch that needs time-stretching, not shifting. This tool handles the common constant-offset case.
Do positive and negative shifts move subtitles which way?
A positive shift delays the subtitles so they appear later, use it when captions are running ahead of the speech. A negative shift moves them earlier, use it when captions lag behind. If a line reads at 00:10 but should read at 00:12, shift by +2 seconds.
Does shifting change how long each caption stays on screen?
No, the start and end of every cue move by the same offset, so each caption's duration is unchanged. Only the whole track slides earlier or later along the timeline.
Can I enter a fraction of a second?
Yes, the shift accepts decimals, so you can nudge by 0.5 or 1.25 seconds. Internally the timestamps are handled in milliseconds, so sub-second corrections are applied precisely.
Are my subtitles uploaded?
No, the shift is calculated in your browser and nothing is sent anywhere. It works offline.