Add Audio to Video — Replace or Overlay Audio Tracks

Add background music, replace the audio track, or overlay narration on any video file. Browser-based processing, no uploads required.

Add audio is a Professional feature. Upgrade your plan to access it.

The Video Downloader Plus add audio tool lets you replace a video’s existing audio track or mix in a new one — background music, narration, or any audio file. All processing runs locally in your browser.

How to add audio to a video

1. Open the tool

   Go to vidow.io/tools/add-audio.

2. Upload your video

   Click Upload video or drag a video file onto the page.

3. Upload your audio file

   Click Upload audio and select the audio file you want to add.

4. Choose a mode

   Select Replace to swap out the existing audio track, or Overlay to mix the new audio with the original.

5. Adjust timing

   Set the offset for when the audio should start relative to the beginning of the video.

6. Export

   Click Export. The output file is saved to your downloads folder.

Supported formats

	Formats
Video input	MP4, WebM, MKV, MOV
Audio input	MP3, AAC, M4A, WAV, FLAC
Output	MP4, WebM

Audio modes

Mode	Description
Replace	Removes the original audio track and replaces it with the uploaded audio file
Overlay	Mixes the new audio with the existing audio track at equal volume

How it works

Audio processing runs locally in your browser using a WebAssembly build of FFmpeg. The tool muxes your audio file into the video container without re-encoding the video stream, keeping processing fast and preserving video quality. No data is uploaded to any server.

Related tools

Merge Videos

Join multiple clips before adding audio.

Video Trimmer

Trim your video to the right length first.

Video Compressor

Reduce file size after adding the audio track.