Fix sound that is out of sync
Choose the video, say if the sound is early or late, and download the fixed file.
The sound is
Making talking videos?
Lip sync made from your audio starts in sync, so there is nothing to fix.
One photo of the host
A sharp, front facing photo. Yours, or one you have the rights to.
Your audio or a typed script
The mouth, jaw and head are generated from the sound itself.
2 credits a second
A 30 second clip is 60 credits, and the cost shows before you make it.
How the sync fixer works
It runs in your browser. Nothing is uploaded.
- Step 1
Choose the video
Drop it on the tool or pick a file, up to 250 MB and 10 minutes.
- Step 2
Say how far off it is
Watch a clap or a hard consonant such as p or b. If you hear it before you see it, the sound is early; after, it is late.
- Step 3
Download and check
The picture and sound are copied, not re encoded, so it takes seconds. If it is still off, try the next step.
Offset or drift?
Check the first and last few seconds before choosing. This tool fixes an offset: the whole soundtrack moves by the amount you pick.
How it works
FFmpeg reads the file twice and delays one copy with its itsoffset option: the sound when it is early, the picture when the sound is late. The two streams are then copied into one file without re encoding, so nothing loses quality.
Use it from an AI assistant
Every setting is a URL parameter, so an assistant can send a link with the options already chosen.
- shift: -0.5, -0.3, -0.2, -0.1, 0.1, 0.2, 0.3, 0.5 (default 0.2). The sound is
Sound is 0.2 seconds early: https://percify.io/tool/fix-audio-video-sync?shift=0.2
Sound is 0.3 seconds late: https://percify.io/tool/fix-audio-video-sync?shift=-0.3
Every free tool and its parameters, as JSON: percify.io/tools.json. Platform facts checked on 17 September 2026 against each platform’s own help pages.
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OpenQuestions, answered
How do I fix audio that is out of sync with the video?
If the sound is early or late by the same amount all the way through, shift it: choose the video, pick Early or Late and the amount, and download. If it drifts further out over time, that is a frame rate problem instead.
How do I know if the sound is early or late?
Watch a clap, a door closing or a p, b or m sound. If you hear it before you see it, the sound is early. If you see it first, the sound is late.
Does fixing the sync reduce quality?
No. The picture and sound are copied, not re encoded; only their timing changes.
Why is my AI dubbed or lip synced video out of sync?
Usually the audio was trimmed, sped up or replaced after rendering. Rendering again from the final audio is the cleanest fix; for a constant offset, this tool shifts it.
Is my video uploaded?
No. It is processed on your device with FFmpeg running in WebAssembly.
