Sync Audio and Video Online – Free, No Upload | sync.video

# sync.video > Fix audio delay, sync a separate mic or several cameras by their sound, and export one file. Free in your browser, nothing uploaded, no watermark. sync.video is a set of browser tools for timing problems in video. Fix audio delay opens one video, finds how far its sound is early or late (automatically from claps and sharp sounds, or by eye with slow motion and frame stepping), corrects steady drift with two sync points, and writes a new file in which the picture is copied untouched and, when only the timing changes, the sound too (the shift is stored in the file’s edit list). Sync separate recordings takes up to eight videos and sound files, matches them by their sound (envelope cross-correlation refined with GCC-PHAT, drift measured in parts per million), and exports one video with the sound replaced, mixed or kept as separate tracks, synced copies, or FCPXML, Premiere XML and CSV timelines. The Sync player plays the same video on many devices in step: each device opens its own copy of the file, one starts a room with a six-character code, and play, pause and seek are shared through peer-to-peer WebRTC data channels with clock synchronisation (a small signalling relay introduces the devices; only control and timing messages travel, never the video). Beat sync finds a song’s tempo and beats and cuts clips or photos on them; the BPM finder, tap tempo, audio delay test, clapperboard and subtitle sync (SRT, VTT, ASS) are smaller tools. Everything runs in the browser with WebCodecs and mediabunny; there is no upload, API, account or server-side processing of files. ## The four tools - [Sync audio and video online](https://sync.video/): The main tool: one video to fix its delay, or several files to line up by their sound, with how the offset is found. - [Fix audio and video out of sync](https://sync.video/fix-audio-sync): Work out whether the file or the playback is at fault, then fix the delay or measure it. - [Sync multiple cameras and recorders

{ "openapi": "3.1.0", "info": { "title": "sync.video public content API", "version": "1.0.0", "description": "Free in-browser tools for timing problems in video: fix a video’s audio delay or drift, line up a separate microphone or several cameras by their sound, play one video in sync on many devices, cut clips to a song’s beat, find a BPM, test a TV’s audio delay and sync subtitles. Nothing is uploaded. Everything here is read-only, public and unauthenticated; the video to