Drop a file here or click to choose
Your file stays on your device. Processing happens locally in your browser.
What is Add Audio to Video?
Add Audio to Video puts a song, background music or a voice-over on a video. Mix it with the original sound or replace it, choose the second where it starts, set both volumes and add fades. Audio that is shorter than the video can stop or loop; longer audio is cut at the end of the video. The picture is copied without re-encoding whenever possible. Both files stay on your device.
Add background music or a voice-over to a video. Mix it with the original sound or replace it, set where it starts, both volumes and fades. Runs locally in your browser with WebAssembly.
Key features
- Mix with or replace the original sound
- Audio start time, new and original volume (0–200%)
- Fade in and fade out
- Loop or stop audio that is shorter than the video
- Picture copied without re-encoding when possible
- Preview both files together before processing
- Runs in your browser — nothing is uploaded
Popular uses
- Add background music to a slideshow or travel video
- Lay a voice-over on a product demo
- Put a song on a silent clip for Status or Reels
Supported formats
Video: MP4, M4V, MOV, WebM, MKV, AVI. Audio: MP3, WAV, M4A, AAC, OGG, Opus, FLAC. Output keeps the video's format (AVI becomes MP4).
Troubleshooting
- The music is too loud over the voices Lower New audio volume (for example to 30–50%) and keep Original sound at 100%.
- The music stops before the video ends Choose Loop it under 'If the audio is shorter than the video'.
Also known as: Add Music to Video, Put Song on Video, Video Audio Mixer.
How it works
- Choose a video, then an audio file (MP3, WAV, M4A, AAC, OGG, Opus or FLAC). Both stay on your device.
- Set where the audio starts, both volumes and optional fades; loop or stop audio that is shorter.
- Preview, click Run and download. The picture is copied without re-encoding when possible.
FAQ
What happens if the music is longer than the video?
It is cut at the end of the video. If it is shorter, it either stops or loops — your choice.
Is my video uploaded?
No. Add Audio to Video runs entirely in your browser with WebAssembly. Your files never leave your device and are never sent to Fah Swe servers.
Can I use any song?
The tool works with any audio file you have, but only use music you have the rights to — platforms may mute or remove videos with copyrighted songs.
Will the video quality change?
No, in most cases the picture is copied as-is. Only files whose video can't be stored with the new audio are re-encoded to MP4, and the notes tell you.