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SRT Shifter & Converter

Shift subtitle timings, fix frame-rate drift and convert between SRT and WebVTT — free, instant and entirely in your browser.

Nothing is uploaded: your subtitles are processed on this device.

How to use the SRT shifter

  1. Paste or open your file. Both SRT (00:00:01,000) and WebVTT (00:00:01.000) timestamps are recognised. Styling tags and line breaks are kept.
  2. Enter an offset in seconds. Use a positive number if the subtitles appear too early, and a negative number if they appear too late. Decimals are fine: -0.25 moves everything a quarter of a second earlier.
  3. Optionally start from a later caption. If only the second half of a file is out of sync (for example after an edit), set "Only from caption #" to the first caption that needs moving.
  4. Fix frame-rate drift. If the subtitles start in sync but slowly drift further out, the file was probably timed for a different frame rate. Pick the matching conversion to stretch or squeeze every timestamp proportionally.
  5. Choose an output format and press Apply, then download or copy the result.

Constant offset or drift?

Check the first and last line of dialogue. If both are out by the same amount, you need a simple shift. If the gap grows through the video, you have drift, which usually comes from a frame-rate mismatch such as 23.976 fps vs 25 fps — a difference of about 4%, or roughly two and a half minutes over an hour. Our guide on why subtitles drift out of sync explains how to diagnose both problems, and frame rates explained covers where those numbers come from.

SRT vs WebVTT

SRT is the most widely supported subtitle format for editors and YouTube uploads. WebVTT is the web standard used by the HTML <track> element and many players. The converter adds the required WEBVTT header, switches the decimal comma to a full stop and removes it again when converting back. For a detailed comparison see SRT vs WebVTT vs ASS.

FAQ

Are my subtitles uploaded anywhere?

No. The tool is a few lines of JavaScript that run in your browser. You can even disconnect from the internet after the page loads and it will still work.

What happens if a shifted caption would start before zero?

It is clamped to 00:00:00,000, and its end time is kept after its start time, so the file stays valid.

Are captions renumbered?

Yes. SRT output is always numbered sequentially from 1, which fixes files with missing or duplicate numbers.

Can I check whether my captions are too fast to read?

Yes — paste the result into our Caption Speed Checker.