---
title: "About sync.video: sound and picture, lined up locally"
description: "Why sync.video exists, how it finds offsets, keeps devices in step and finds beats in a browser, and its promises: free, no uploads, no watermark, no account."
url: https://sync.video/about
---

# 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](https://sync.video/privacy), and you can reach us through the[contact page](https://sync.video/contact).