sync.video is a free set of browser tools for getting sound and picture back in step. Fix audio delay opens a video on a waveform timeline: Detect automatically matches claps and sharp sounds to changes in the picture, or you mark the clap frame, then nudge the sound in 1 ms steps and check at half or quarter speed. Export copies the picture frame for frame, so there is no quality loss. Sync separate recordings lines up a camera with a separate mic, or up to eight angles, by their sound, with FCPXML or Premiere XML export. Nothing is uploaded; no account, no watermark.
Lining up audio by hand in an editor is slow, and dedicated sync tools are paid desktop software. sync.video was built so creators can fix lip-sync or sync a separate microphone in a browser tab, free, without uploading their footage.