Slimvid

Add Audio to Video Online

Put music or a voiceover under your video. Replace the original track or mix them together.

Drop a video here, or click to browse

Up to 1GB each · MP4, MOV, WebM, MKV, AVI, WMV and 30+ more

Choose file

Processed locally in your browser. Nothing is uploaded.

Settings

Add a video and the settings for this tool appear here.

How it works

  1. 1Drop your video, then add the audio file (MP3, M4A, WAV, etc.).
  2. 2Choose Replace to swap the soundtrack or Mix to blend it with the original.
  3. 3Merge and download. The video track is copied without re-encoding.

Processed locally in your browser. Nothing is uploaded.

Three steps

How to add audio to a video

No sign-up, no upload queue, no watermark. Everything happens on your device.

  1. 1

    Drop your file

    Drop your video, then add the audio file (MP3, M4A, WAV, etc.).

  2. 2

    Choose settings

    Choose Replace to swap the soundtrack or Mix to blend it with the original.

  3. 3

    Download

    Merge and download. The video track is copied without re-encoding.

Keep going

Related tools

FAQ

Add Audio FAQ

Desktop app

Files over 1GB? Take it to the desktop.

The browser version is perfect for everyday clips. When you need to crunch big footage or dozens of files, the desktop app does it faster on your own hardware.

Get early accessCompare web vs desktop
  • No file size limit — 4K, hour-long recordings, anything
  • Batch queues: drop a folder, apply one preset
  • Hardware-accelerated encoding (H.264 / H.265)
  • Works fully offline, same privacy guarantee