OneTaskBy Tim King · Updated
SRT Timestamp Shifter
Shift Subtitles Earlier or Later From Any Cue in an SRT or VTT File
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How the SRT Timestamp Shifter works
This SRT timestamp shifter fixes subtitles that are early, late or drifting. Paste an SRT or WebVTT file, enter how many seconds to move it, and copy the corrected file. You can shift only from a chosen cue onwards, or rescale every time for a frame-rate mismatch. Nothing is uploaded.
Subtitle files store an exact start and end time for every line. If those times were made for a slightly different cut of the video, every line appears at the wrong moment, even though the text is perfect. There are three common patterns, and each has a different fix.
What the SRT timestamp shifter fixes
| Symptom | Likely cause | Fix |
|---|---|---|
| Every line is late by the same amount | Intro, logo or recap added | Negative shift |
| Every line is early by the same amount | Intro or recap removed | Positive shift |
| Fine at first, then off from one scene | Ad break or scene removed | Shift from that cue |
| Gap grows steadily through the film | 23.976 vs 25 fps versions | Frame-rate correction |
Constant offset. Find a line you can hear clearly, note when it is spoken and when the subtitle appears, and shift by the difference. If the subtitle shows at 00:01:12 but the line is spoken at 00:01:10, enter -2.
Offset from one point. Set "Start at cue number" to the first cue that is wrong. Earlier cues are left exactly as they were, and that cue and every later one move by the shift.
Steady drift. European TV and DVD releases run film at 25 frames per second, about 4% faster than the 23.976 used for cinema and streaming. Subtitles timed for one play progressively out of sync on the other: by the end of a 2-hour film the error is almost 5 minutes. The correction multiplies every time by the ratio of the two rates, so 23.976 to 25 multiplies by 0.959.
How it works
The tool reads each timing line, 00:01:12,500 --> 00:01:15,000, converts both times to
milliseconds, applies the frame-rate factor and then the shift, and writes them back in the same
format. SRT keeps comma decimals and WebVTT keeps dots. Cue numbers, text, styling tags and VTT cue
settings such as line:10% are passed through untouched. Any time that would fall before zero is
clipped to 00:00:00,000 and counted in the stats.
Tips and pitfalls
Test with two lines. Check one line near the start and one near the end after shifting. If the start is right but the end is off, you need the frame-rate correction, not a bigger shift.
Apply the rate first. When you need both, choose the frame-rate correction and the shift together. The tool scales first and then shifts, so the offset you measured is not stretched.
Save as UTF-8. Paste from a text editor that reads the file correctly. Accented characters that already look broken in the editor will stay broken.
How to read the result
The stats show the format detected, how many cues were changed and the new start of the first changed cue. Copy or download the corrected file and save it with the same name as the video.
FAQ
How do I know how much to shift my subtitles?
Pick a clear line of dialogue. Note the time it is spoken in the video and the time its subtitle appears in the file. Subtract the subtitle time from the spoken time and enter the result: negative when the subtitles are late, positive when they are early.
Why are my subtitles more out of sync as the film goes on?
The subtitles were timed for a version with a different frame rate, usually 23.976 against 25 frames per second. A fixed shift cannot fix that. Choose the matching frame-rate correction so every time is scaled by the right ratio.
Does it work with VTT files as well as SRT?
Yes. A file that starts with WEBVTT is treated as WebVTT and keeps dot decimals and any cue settings. Anything else is treated as SRT. To change the format as well, use the SRT to VTT converter.
Is my subtitle file uploaded?
No. The text you paste is processed by JavaScript in your own browser and never sent to a server, so unreleased scripts and private transcripts stay on your device.
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