About sync.video
Few things make a video feel cheaper than sound that doesn’t match the picture. A voice that arrives a beat after the lips move, a clap you hear before you see it, a band whose drummer hits the snare a moment after the sound. Most of the time the fix is a number of milliseconds, but finding that number, and saving a file with it, usually means installing an editor, learning its timeline and exporting the whole video again. sync.video exists to make that a two-minute job in a browser tab, with nothing uploaded.
What it does
- Fix audio delay in one video: find the offset, check it in slow motion, correct slow drift and save a new file.
- Sync separate recordings: line up a camera with a separate microphone or recorder, or several cameras, by their sound; replace or mix the sound; hand a ready-made timeline to an editor.
- Sync player: play the same video on many phones, laptops and TVs in step, for watch parties, video walls and classrooms.
- Beat sync: cut clips and photos to a song’s beats, with a BPM finder and tap tempo alongside.
- Smaller tools for the jobs around them: an audio delay test for headphones and TVs, a clapperboard for the start of a take, and subtitle sync for SRT and VTT files.
How it works
Everything runs in your browser. Files are read with WebCodecs and the mediabunny library; sound is analysed in a background worker, where waveforms are matched with fast Fourier transforms and a technique called GCC-PHAT that lines recordings up to a fraction of a millisecond. When only timing changes, the new file is made by copying the original compressed picture and sound with new timestamps, so nothing is re-encoded and nothing is lost. Files your browser can’t read are converted on your device by a copy of ffmpeg that the site serves itself.
The sync player is the one tool that needs devices to talk to each other. A small relay on our hosting introduces the devices in a room, then they exchange play, pause and clock messages directly where the network allows. The video itself is never sent: every device plays its own copy.
What it promises
- Free, with no watermark, no account and no adverts.
- Your videos, recordings, songs, photos and subtitles stay on your device.
- Analytics that count visits and features, never your files, and that you can switch off under Cookie settings.
- Honest answers: every automatic result comes with a confidence figure, and the guides say when a built-in setting or another app is the better route.
Who it’s for
Video makers syncing a lav mic or a second camera, podcasters with a separate recorder, teachers and churches running the same video on several screens, friends watching a film together from different homes, people cutting a holiday reel to a song, and anyone whose TV or headphones make everything sound late.
sync.video is an independent, self-funded project. How your data is handled is set out in the privacy policy, and you can reach us through the contact page.