Subtitle timing fixer

What it does

Shift SRT or WebVTT subtitles and correct gradual timing drift, then export repaired timestamps.

How to use it

1. Paste subtitles or open an SRT/WebVTT file. Positive shift moves cues later; negative shift moves them earlier.
2. Drift is the additional correction in seconds at one hour, applied proportionally from time zero. For +2 seconds at the start and +5 at one hour, use shift +2 and drift +3.
3. Up to 500,000 characters or a 2 MB input file. Shift is limited to ±86,400 seconds and drift to ±600 seconds per hour. Negative output timestamps are rejected.

Example

Shifting a cue at 00:00:10,000 by +2 seconds moves its start to 00:00:12,000.

Methodology

Each timestamp becomes original × (1 + drift / 3600) + shift, rounded to milliseconds. Cue text and WebVTT settings are retained; line endings are normalised.

Limitations

No speech recognition, translation or media playback. Output timestamps must remain below 100 hours and end after start. Existing overlaps are preserved; unsupported or malformed timing lines are rejected.

Automation

This tool runs in your browser. No upload API or MCP endpoint is available.