How do I fix subtitles that gradually fall out of sync?

Subtitles that start in sync but gradually drift ahead or behind suffer from a framerate mismatch. This typically occurs when subtitles authored for 23.976 FPS theatrical film are played against 25 FPS PAL television video. Use the Framerate Converter dropdown in SubRip Sync to multiply the timing by the exact ratio (23.976 / 25 or 25 / 23.976) to permanently fix the drift across the entire movie.

Are my subtitle files uploaded to a server?

No. SubRip Sync is a 100% client-side WebAssembly and JavaScript utility. Your subtitle files are parsed and modified entirely inside your browser memory and never leave your computer.

What is the difference between SRT and WebVTT timestamps?

SubRip (.srt) uses commas to delimit milliseconds (e.g., 00:01:23,456), while WebVTT (.vtt) uses periods (e.g., 00:01:23.456). SubRip Sync automatically detects the format, preserves proper formatting, and prevents file corruption.

Free Subtitle Time Shifter & Sync Calculator

Re-time, Shift & Fix Subtitle Delays

Shift timestamps earlier or later, fix framerate conversion drift (23.976 ↔ 25 FPS), or apply 2-point linear alignment. Files never leave your browser.

Video Editing Tools Explore AI automatic subtitle generators, video editors, and sound design plugins.

1. Select Subtitle Source

↑

Click or Drag & Drop File

Accepts .srt and .vtt files

sample_subtitles.srt

2. Timing Adjustment

Time Shift (+ / -)

Quick Jumps:

Live Timestamp Difference Inspector

4 cues detected | SRT

How Subtitle Synchronization & Framerate Drift Work

1. Fixed Audio Delays vs Framerate Drift

Subtitle desynchronization comes in two distinct types:

Constant Offset: Subtitles are off by the exact same amount from start to end (e.g., exactly 1.5 seconds early due to a studio logo bumper). A simple addition/subtraction fixes it everywhere.
Progressive Drift: Subtitles start perfectly synchronized during the opening scene, but by minute 45 they are 3 seconds off, and by hour 2 they are 8 seconds off. This is caused by a framerate mismatch.

2. The 23.976 to 25 FPS PAL Problem

Theatrical movies shot at 23.976 or 24 FPS are traditionally sped up by 4.27% when broadcast on European 25 FPS television (PAL standard).

If you load theatrical subtitles onto a PAL broadcast rip, the video finishes faster than the subtitles. By applying our 1.042709x multiplier, all timestamps scale proportionally to match the video.

Frequently Asked Questions

How do I shift subtitles that appear too early? ▾

If subtitles appear before the actor speaks, enter a positive value (e.g. +1000 ms or +1.5 seconds). This pushes all dialogue cues further into the future to match speech.

Will this damage character formatting like italics or bold tags? ▾

No. The engine selectively modifies timestamp lines matching the standard SMPTE timecode patterns while preserving all HTML formatting tags (<i>, <b>, font colors) and subtitle IDs verbatim.

What happens if an offset pushes a subtitle before 00:00:00? ▾

Timestamps are clamped to zero (00:00:00,000). Negative timecodes are invalid according to the SubRip and W3C WebVTT specifications and cause video players like VLC, Plex, or QuickTime to crash or skip playback.