Subtitle Out of Sync? How to Time-Shift SRT/VTT/ASS (Plus Overlap Fix Tips)

TL;DR

• Shift subtitles forward/backward in seconds with Subtitle Time Shift—works for SRT/VTT/ASS.
• Clamp negative times to 0, and auto-trim overlaps to avoid double cues.
• Spot-check the start, middle, and end after shifting; then export clean .srt, .vtt, or .ass.

Why Subs Go Out of Sync

• Different frame rates or transcoding drift.
• Edits to audio/video after the subtitles were made.
• Player adds/removes intro/ads; you need a consistent offset.

The Core Fix: Apply an Offset

• Positive offset (+ms/sec): subtitles appear later.
• Negative offset (−ms/sec): subtitles appear earlier.
• Clamp to 0: prevent negative start times after a backward shift.

Handling Overlaps

After shifting, cues can collide (end > next start). Auto-fix by:

1. Trim ends: set end = min(end, nextStart - gap) where gap is small (e.g., 50–100ms).
2. Drop zero-length cues: if end <= start, remove or stretch minimally.
3. Normalize gaps: keep small gaps between cues to avoid flicker.

Quick Examples

• Need subs 1.2s earlier: apply -1200ms.
• Need subs 900ms later: apply +900ms.
• Overlap fix: ensure each cue ends before the next starts; add a tiny gap.

How to Fix in Seconds (Browser-Only)

Use Subtitle Time Shift:

• Upload SRT/VTT/ASS.
• Enter offset (+/- ms/sec).
• Enable “fix overlaps” to auto-trim end times.
• Preview, then download corrected subs (files stay on your device).

Best Practices

• Test at 3 points: early, mid, late—drift can change across the video.
• If drift worsens over time, try re-encoding or re-timing with a linear ramp (not just a flat offset).
• Keep a backup of the original file before trimming overlaps.

FAQ

Do you upload my subtitles?
No. Processing runs locally in your browser.

Which formats are supported?
SRT, VTT, and ASS for shifting; outputs match your input format.

Will styling be preserved?
ASS styling stays; SRT/VTT remain plain text; only timing shifts.

Can I batch files?
One at a time; you can run multiple files quickly in-browser.

Ready to resync?

Try Subtitle Time Shift and export fixed subtitles in seconds.