Add audio to a video
Put music or a voice-over on a video, or replace its sound. The picture is copied as it is, and nothing is uploaded.
- Nothing is uploaded
- Works offline after first visit
- Open source
- No watermark · limit is your device’s memory; phones hold less
Puts an MP3, WAV or M4A track on a video, or swaps in the sound of another clip, and saves a new video. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. The size limit is your device’s memory, and phones hold less; give the page a short while after one visit to save itself for offline use, and then it works offline.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
How it works
- Drop a video (MP4, MOV, WebM or MKV) and a sound file (MP3, WAV, M4A, or another video).
- Choose whether the new sound replaces the video’s own sound or plays quietly underneath it.
- Add audio. The picture is copied without re-encoding and the new sound is laid under it, looped or cut to fit.
In your browser, not on a server
Mediabunny (MPL-2.0) reads the MP4, MOV, WebM or MKV video in your tab and copies its picture packet by packet into a new file, with no re-encoding. The sound file is decoded by your browser, looped or cut and faded to the length of the video, mixed with the video’s own sound if you asked, and encoded as AAC (or Opus) by your browser (WebCodecs).
Compared with upload-based tools: Online editors upload the video and the song to a server, re-encode the whole picture, cap free exports and often add a watermark. Here nothing leaves your device and the picture is not touched.
Verify it yourself. Give the page a short while after one visit to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Are my files uploaded?
No. Your browser decodes the sound, fits it to the video and writes a new file in this tab. There is no upload and no watermark.
Does the video lose quality?
No. The picture is copied packet by packet, exactly as it was, so it takes seconds and nothing changes. Only the sound is encoded again, as AAC in an MP4 (or Opus in a WebM for VP8 videos).
What if the song is longer or shorter than the video?
A longer sound is cut at the end of the video and faded out. A shorter one is repeated until the video ends, or, with Loop unticked, the rest of the video is silent.
Can I keep the original sound and add music under it?
Yes. Choose Keep it, with the new sound quieter underneath: the music plays at half volume under the voices in the video.
More video and audio tools
Reverse video
Make a clip play backwards, for a rewind effect, a boomerang or a laugh. Done on this device, never uploaded.
Video to JPG
Turn a video into still images: a few good frames or every single one. Done on this device, never uploaded.
Trim audio
Cut a song, a voice memo or a podcast down to the part you want, with fades if you like. Done on this device, never uploaded.
Audio converter
Turn any sound file into MP3, WAV, FLAC, M4A or OGG. Your files are converted on this device and never uploaded.
Popular conversions
Guides
- How to add music to a videoAdding a soundtrack to an existing video is not something most camera rolls support directly. Here is what does the job.