Change a video’s audio track
Mute a clip before sharing it, or lay narration over screen recording. The picture is never re-encoded, so a two-minute video takes seconds, not minutes.
- Runs entirely in your browser
- Works offline
- No upload
- No sign-up
- No watermark
Loading the tool…
How it works
- Drop the video.
- Choose remove, or choose replace and pick the audio file.
- Start — the video stream is copied as-is.
Why nothing is uploaded
Every operation on this page is done by code running inside your browser tab, using the same engine that renders web pages. The file is read from disk into your tab’s memory, transformed there, and written back out as a download. It is never sent anywhere — not to us, not to a third party.
Verify it yourself
- Open your browser’s developer tools (F12) and select the Network tab.
- Load your file and run the tool.
- The only requests you will see fetch the tool’s own code — and, for a few heavy tools, their open-source engine from a public CDN — plus one small page-view ping to loreatec.jp (page address and title, nothing more). None of them carry your file.
Frequently asked questions
Why is this so much faster than converting?
Because the video — the heavy part — is copied byte-for-byte, not decoded and re-encoded. Only the audio is touched. That also means zero quality loss on the picture.
What happens when the audio and video lengths differ?
The output stops at the shorter of the two. A 3-minute song over a 1-minute clip gives a 1-minute video; if you need the music to loop or the video to hold, do that in an editor first.
Why did my file fail with “codec not supported in container”?
Copying the video stream means the output container must accept the original codec — MP4 will not take VP9, for example. Choose MKV, which accepts nearly everything, or convert the video properly instead.
Is my video uploaded?
No. The video engine is compiled to WebAssembly and runs inside this tab; the file is read from disk into memory and the result is written back out. Nothing is transmitted, which is why a two-hour film will not work here — your device is doing all of it.