Subtitle Sync Shifter
Shift all SRT and WebVTT subtitle timestamps by a fixed offset, or linearly rescale between two anchor points to fix drift. 100% in-browser, free, no upload.
Loading tool...
What is Subtitle Sync Shifter?
Subtitle Sync Shifter is a free online tool that fixes out-of-sync subtitle files. It shifts every cue timestamp in an SRT or WebVTT file by a constant offset, or linearly rescales timings between two anchor points when subtitles drift progressively. Everything runs locally in your browser — no upload, no account, no limits.
Key Benefits
- Fix subtitles that display too early or too late in seconds
- Correct progressive drift with two-anchor linear rescaling
- Preserve all cue text and formatting exactly as-is
- Keep files private — nothing is uploaded anywhere
- Free with no cue-count or file-size limits
Common Use Cases
- •Syncing subtitles downloaded from a different frame-rate release (23.976 vs 25 fps)
- •Fixing subs that start fine but end several seconds off
- •Re-aligning captions after trimming an intro from a video
- •Adjusting SRT/VTT files for a different cut of a film
How to Use Subtitle Sync Shifter
- Paste or upload subtitles: Paste your .srt or .vtt content into the input box, or click the upload button to load the file directly. The tool detects the format automatically.
- Pick an adjustment mode: Choose "Shift all timestamps" for a constant offset, or "Linear rescale" when subtitles drift progressively out of sync toward the end.
- Set the timing correction: Enter an offset in milliseconds or seconds (negative to move subtitles earlier), or fill the two anchor pairs with the current and correct times of a cue near the start and near the end.
- Check the preview and download: Review the first/last cue before-and-after timings, then click Download to save the fixed file or Copy to paste it elsewhere.
Key Features
- Constant shift mode with millisecond precision for simple early/late offsets.
- Linear rescale mode using two anchor cues to correct progressive drift.
- Auto-detects SRT and WebVTT and keeps the correct timestamp separator style.
- First/last cue preview to sanity-check timings before downloading.
- Copy or download the fixed subtitle file with one click, fully client-side.
Frequently Asked Questions
What does the Subtitle Sync Shifter do?
It rewrites every cue timestamp in an SRT or WebVTT file so subtitles line up with your video again. You can shift all timings by a constant offset (for subtitles that are uniformly early or late) or linearly rescale between two anchor points (for subtitles that drift progressively).
How do I know if I need a constant shift or a linear rescale?
Play the video and check a subtitle near the beginning and another near the end. If both are off by the same amount, use a constant shift. If the error grows toward the end (e.g. 1 second early at first, 10 seconds early by the end), use linear rescale with two anchors.
Are my subtitle files uploaded to a server?
No. All parsing and rewriting happens locally in your browser with JavaScript. Your files never leave your device, which makes the tool safe for private or unreleased content.
Which subtitle formats are supported?
SRT (SubRip, comma milliseconds) and WebVTT (.vtt, dot milliseconds) are fully supported, including VTT cue settings after the end timestamp. Cue text, positioning, and styling are preserved exactly; only the timestamps change.