Replace audio
Swap the soundtrack. Drop the clip first, then the new audio.
Runs in this tab. The file stays here.
This runs in your browser. Nothing is uploaded. Longer clips take longer here than they would on a fast server — that is the trade-off for not sending the file.
About Replace audio
Swaps the soundtrack of a clip in the browser. Drop the video first, then the new audio. Nothing is uploaded.
The picture is copied when the container allows it; audio is encoded to fit MP4 or WebM. The result is cut to the shorter stream. If you need the picture to hold on a still while audio continues, that is a different editor. Drop order matters: clip first, then the new soundtrack.
Replace audio runs FFmpeg compiled to WebAssembly in this tab. The first visit of a video or audio tool fetches about 30 MB from this origin; after that it can stay cached. Your file is not in that download and is not POSTed anywhere. GPL FFmpeg, single-thread, same origin, no COEP experiment. That is the same encoder as convert, trim, and compress — this page is just a different argument list, with the same honesty about what the core cannot mux.
You can open the network panel and watch. Encoding a long clip on a phone is slow because it is your CPU. That wait is the trade for not handing the file to a converter you found in a search ad. Reverse and boomerang cap duration so a two-hour file does not try to live backwards in RAM. If a codec inside a familiar extension is missing from this core, you get an error rather than a silent broken file. Subtitle generation and stem splitting are not here; I will not pretend they are. Missing is better than a watermarked demo.
How to use Replace audio
- 1Drop the clip, then the audio file.
- 2Click Replace audio, then download.
What it won't do
- Two files required.
- No mix, only replace.
Common questions
Does replace-audio upload the files?
No.
What if the audio is longer than the video?
-shortest wins. Extra audio is dropped.
Can I mix instead of replace?
No. The old track is discarded. Mixing two beds is a DAW job.
Related tools
Why this one doesn't upload your file
There is no server to upload to. This page is a static file, and the work happens in your browser using the same graphics and WebAssembly code that renders every other site you visit. Your file is read from disk into memory, processed, and handed back as a download. Once the page has loaded you can disconnect from the network entirely and it keeps working. The longer explanation