Lip Sync
Lip sync rebuilds the mouth in a video so it matches an audio track you supply. The rest of the frame — the body, the head movement, the background, the lighting — stays as you filmed it, and only the mouth region is regenerated to fit the new speech. It is the narrowest of the six jobs here and, because of that, the most reliable.
The usual reasons to reach for it are dubbing into another language, replacing a line that was delivered badly, and fixing footage where the audio drifted out of sync. This route is not connected yet — the controls and prices are real, the Create button is not.
Why this one holds up better than the others
Every other generative tool in this studio regenerates the whole frame, which is why faces drift and backgrounds warp. Lip sync changes a small region and composites it back, so the person stays recognisably themselves and the shot stays your shot.
The practical consequence: you can use it on footage of real people at a quality the other tools cannot reach — and that is also exactly why it needs the clearest limits on what it may be used for.
What the source video needs
The mouth has to be visible, reasonably large in frame, and roughly front-on for most of the clip. The model is rebuilding a region it can see; the less of that region is visible, the more it invents.
- The face facing the camera within about 30 degrees. A subject in profile has no mouth shape to work from.
- The mouth unobstructed throughout — no hand over the face, no microphone across the chin, no hair falling across the mouth.
- One speaker in frame. Two faces means the model has to guess which one is talking.
- Enough resolution that the mouth is more than a few dozen pixels across. A wide shot of someone at the far end of a room will not work.
- Steady framing. Fast cuts within the clip break continuity; sync each shot separately.
What the audio needs
Clean speech with as little behind it as possible. The model is deriving mouth shapes from the sound, and music, room reverb or a second voice in the background all degrade that derivation before generation even starts.
Match the length to the clip. Audio longer than the video leaves speech with no frames to land on; audio shorter leaves the mouth to idle at the end. Trim both to the same duration first.
Pace matters as much as cleanliness. Speech noticeably faster than natural delivery produces mouth movement that reads as mechanical, because the shapes have too few frames each to resolve.
Dubbing into another language
This is the most common real use, and the one where expectations need setting. The mouth will match the new language, and the rest of the performance will not — gestures, head movement and expression still belong to the original delivery, and languages differ in rhythm enough that a mismatch is sometimes visible.
It works best when the translated line is close in length to the original. A translation that runs forty percent longer forces speech into the same number of frames, and the result reads as hurried regardless of how good the sync is. Ask a translator for a length-matched line rather than a literal one.
When not to use this
- Making a real person appear to say something they did not say. This is the clearest misuse of the tool and the reason it needs stating plainly: use it on footage of someone who agreed to be dubbed, for words they agreed to.
- Anything presented as genuine record — news footage, testimony, evidence, a public figure’s statement.
- Profile shots or faces turned away. There is no mouth region to rebuild.
- Wide shots where the face is small in frame. The mouth needs real pixels to work with.
- Clips with more than one person speaking. Sync one speaker per clip.
- Fixing audio quality. This changes the picture, not the sound; a noisy recording stays noisy and syncs worse.
Questions people ask
What is AI lip sync?
It regenerates the mouth region of a video so the speech shapes match an audio track you supply, leaving the rest of the frame untouched. It is used for dubbing into another language, replacing a badly delivered line, and repairing footage where picture and sound drifted apart.
What video works best for lip sync?
One speaker, face towards the camera within about 30 degrees, mouth unobstructed and large enough in frame to carry detail, with steady framing and no cuts inside the clip. A profile shot or a wide shot of a distant subject will not produce usable sync.
What audio works best?
Clean speech at a natural pace, with no music or background voices, trimmed to the same length as the video. Speech that runs faster than natural delivery produces mouth movement that looks mechanical because each shape gets too few frames.
Can I use it to dub a video into another language?
Yes, and it is the most common use. Get the translated line close in length to the original — a translation running much longer forces the speech into the same frames and reads as hurried. Bear in mind the gestures and expression still belong to the original delivery, so the performance may not match the new language’s rhythm.
Will the person still look like themselves?
Yes, far more than with the other tools here. Only the mouth region is rebuilt and composited back, so identity, lighting and background are your original footage. That is what makes this the most reliable of the six jobs.
Can I lip sync a video of someone else?
Only with their agreement, and never to put words in their mouth that they did not agree to say. Of everything in this studio, this is the tool most easily misused, and that limit is not a formality.
How much does it cost?
The per-clip price of the model you pick, shown on the Create button before you spend anything.
Related tools
Checked 20 September 2026.