How to sync subtitles with a video
- Select your video and your subtitle file.
- The tool listens to the audio, uses speech recognition to find where people talk, and automatically aligns the subtitles with the speech.
- Double-check the timing in the live preview of your video with the synced subtitles.
- Download your correctly synced subtitle file.
What causes subtitles to be out of sync
A subtitle file made for a different release of the same movie or episode is often off by a fixed amount. Every line is a few seconds early, or a few seconds late. That delay (also called the subtitle offset or latency) stays the same through the whole file, which makes it the easiest kind to resync.
If the subtitles start out fine and get worse as the movie goes on, they might have been made for a video with a different frame rate. In that case the lines drift a bit further away from the speech every minute (more on that below).
If the subtitles are in sync for a while and then suddenly jump ahead or fall behind, they might have been made for a version of the video with more or fewer scenes than yours (a director's cut, for example).
Sometimes the subtitles just weren't made right. Even the ones that come with a Blu-ray or are embedded in the video file can be badly synced from the start.
Subtitles that slowly drift out of sync
If the subtitles drift further away from the speech every minute, the frame rate might be wrong. For example, subtitles for a 25 fps release, played with a 23.976 fps video, are about 2.5 seconds early after one minute.
The tool detects frame rates automatically, including all the common ones (23.976, 24, 25, 29.97 and 30 fps), and adjusts the subtitle speed to match your video.
Fix subtitle timing in any language
The tool uses speech recognition to find where people talk. It doesn't understand what's being said, it only hears when someone is talking, and that works the same in any language. By recognizing when people talk and when there's silence, the tool finds the delay automatically. It then adjusts the timing of your SRT file, so you don't have to do any subtitle synchronization by hand.
An online alternative to SubSync
SubSync, the "subtitle speech synchronizer", was a popular desktop app for syncing subtitles to the speech in a video, but it's no longer maintained. This tool does the same job, but it runs in your browser, so there's nothing to install.
Changing the subtitle delay in VLC, Plex or Jellyfin
Most video players, like VLC, Plex and Jellyfin, let you shift the subtitles while you watch. This works for simple shifts, but the fix isn't permanent, and it doesn't help when the subtitles slowly drift out of sync. Instead of adjusting the delay while you watch, use this tool to sync the subtitle file once, for every player.