UseTool

Add music to a video without removing its sound

Keep the original sound and mix music underneath it. Set both volumes and decide whether short music repeats or fades out.

Video

Music

The image track is copied without being recalculated; only the audio track is replaced by the mix.

🔒 Your video and music never leave your device.

How it works

How it works

  1. 1

    Add what goes in

    Add a video and an audio file together — the tool needs both before it can start.

  2. 2

    Start it

    Set the balance between the two sounds, then start. Everything runs in this browser — no upload, no queue, no account.

  3. 3

    Take the result

    The MP4 · WebM is ready the moment the run finishes. Save it straight to your device.

What this tool does

Add music and keep the original sound
Lays a second sound over the one already there, both audible. Unlike replacing the track, the original sound stays — for a commentary over a recording that should keep its own atmosphere.

When you need this

  • A holiday clip should get background music while the children's laughter stays audible.
  • A product demo needs quiet music under the spoken explanation.

Supported formats

MP4MOVWebMMKV + MP3M4AWAVOGGFLAC → MP4WebM

Good to know

Frequently asked questions

What files can I use here?

Reads MP4, M4V, MOV, WebM and 14 more formats. Needs a video and an audio file together.

What do I get back?

You get MP4 · WebM.

Does the file lose quality?

Every frame is decoded and encoded again. That is what makes the file smaller or different — and it costs some detail, most visibly in fast motion and fine texture.

When does it not work?

Which video codecs work depends on your browser. Chrome and Edge read the most, including H.265 on many machines; Safari and Firefox refuse some. A file that will not open here usually opens in Chrome.

Does the video lose quality?

Only when it has to be re-encoded. Cutting, joining and removing the sound track copy the picture data unchanged, so those are lossless. Compressing and adding a watermark do re-encode, which is why they take longer.

How long may a video be?

There is no fixed limit. What decides is the memory of your device: a phone manages a few minutes comfortably, a computer handles far more. If a long video fails, splitting it first and working on the parts usually helps.

Private by design

Your files stay on your device

Your video and music never leave your device.

Other tools

Ready-made

Workflows for this file type