Add Music to Video
Drop in a video and an audio file to put music under it. You can replace the original sound or keep it in the background, loop music that's too short, and fade it out at the end. The picture is copied through untouched, so even large files are done in seconds.
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How to use
- Choose your video, then choose the audio file you want to use.
- Decide what happens to the original sound: replace it, or keep it quietly in the background under the new track.
- Set the volumes, pick whether short audio should loop, then click “Apply audio” and download.
What is this tool?
Add Music to Video swaps or layers the sound track of a video using FFmpeg compiled to WebAssembly. The key detail is that the video stream is copied rather than re-encoded: no frame is touched, so there is no quality loss and no long wait — only the audio is processed, which takes seconds even for a file of several hundred megabytes. In mixing mode the original sound and your new track are combined at volumes you control, which is how you put background music under narration without drowning it out. If the video has no sound track at all, the new audio is simply added. Everything runs on your device, so unreleased footage and licensed music never get uploaded anywhere.
Common uses
- Putting background music under a clip for social media
- Replacing noisy on-camera audio with a clean voice-over recording
- Adding music to a slideshow video that was exported silent
- Laying a soundtrack under a screen recording while keeping the click sounds audible
FAQ
Does this reduce my video's quality?
No. The video stream is copied through frame for frame — only the audio is re-encoded. That is also why it's fast: there is no video encoding involved at all.
What if my music is shorter than the video?
Your choice. “Leave the rest silent” keeps the music as-is and the tail of the video stays quiet; “Repeat until the video ends” loops the audio to fill the whole length. Audio longer than the video is always cut at the end of the picture.
Can I keep the original sound and just add music underneath?
Yes — set “Original sound” to “Keep it and mix”. Two volume sliders appear so you can push the music down under speech. A good starting point is the original at 100% and music around 20–30%.
Which audio formats can I use?
MP3, WAV, M4A, AAC, OGG and FLAC all work. The audio is re-encoded to AAC at 192 kbit/s for the output file, which every player and platform accepts.