Welcome to FFsubsync’s documentation!
FFsubsync performs language-agnostic automatic synchronization of subtitles with video, so that subtitles are aligned to the correct starting point within the video.
Turn this… |
…into this |
|---|---|
|
|
Point it at a video (or a correctly-synced subtitle file) and an out-of-sync subtitle, and it figures out the time offset — and, if needed, a framerate correction — that lines them up:
$ ffs video.mp4 -i unsynchronized.srt -o synchronized.srt
Prefer not to install anything? There is now a browser version that runs ffsubsync entirely client-side via WebAssembly — nothing is uploaded, and your files never leave your machine: https://smacke.github.io/ffsubsync. See In your browser.
The rest of these docs walk from a five-minute quickstart through the more advanced knobs (reference types, voice-activity detectors, the bulk-sync quality gate) and include a deep dive on character encoding, an area where ffsubsync is unusually robust compared to other subtitle sync tools.
New here? Start with Installation and Usage. Looking for a specific flag? Jump to the CLI reference.