Put a music track on a video two ways: mix it underneath the sound that is already there, so speech and background stay audible, or replace the audio outright when the original is not worth keeping. A track shorter than the video can loop to fill it or play once, whichever you pick. The picture is copied across untouched, so video quality is unchanged, and everything runs privately in your browser with nothing uploaded.
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Drop your video here
or click to select a file
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video.mp4
The new track replaces the original audio - it is not mixed over it.
Drag a video onto the upload area or click Select Video. MP4, MOV, MKV and WebM all work, with or without an existing audio track.
Choose the music, then how it should sit
Click Choose Audio and pick an MP3, WAV, M4A, AAC, FLAC or OGG file. Then choose whether to keep the original sound and mix the music under it, or replace the audio entirely. In mix mode you can set how loud the music sits.
Convert and download
Click the button and download the result. The picture is copied rather than re-encoded, so only the audio has to be processed and even a long video finishes quickly.
Mixing music in, or replacing what is there
Most people asking how to add music to a video want the music underneath what they already have: the talking, the room, the game audio still audible, with a bed sitting below it. That is what mix mode does. The default level of 30% is roughly where a bed sits without competing with speech; raise it for something closer to a music video, drop it to 15% if there is dialogue you cannot afford to lose.
A music track is almost never the same length as the footage, so you choose what a short one does. Loop to fill repeats it until the video ends - a two-minute bed under a ten-minute video plays five times rather than leaving eight minutes of silence. Play once is the right answer for anything that is not a bed: a voiceover, an intro sting, a sound effect. A track that runs past the end is trimmed either way.
Replace mode is the other half, and it is the right choice more often than it sounds. When the recorded sound is wind, room echo or the person holding the camera, keeping it under the music helps nobody. Replacing drops the original entirely and puts your track in its place.
When you need to swap a soundtrack
The most common reason is that the recorded sound is simply not usable. A camera microphone picks up wind, room echo, traffic or the person holding it, while a phone or a lavalier recorder sitting closer to the speaker captured the same moment cleanly. Replacing the track puts the good recording over the good picture without touching either one's quality.
The second is silent footage that needs something: a screen recording that captured no system audio, a drone or action-camera clip with nothing but rotor noise, a timelapse that was never going to have sound. Here there is no original track to lose, so dropping in music or narration is purely additive.
The third is licensing and reach. A clip whose background music will be muted or blocked on upload can have that music swapped for something you are cleared to use, before anyone's automated system has an opinion about it. Doing that locally means the footage never leaves your device on the way.
One case is worth naming because it surprises people: a video with no audio at all. There is nothing to mix into, so both modes do the same thing and your track simply becomes the video's soundtrack. Screen recordings that captured no system audio and drone footage are the usual examples.
Frequently Asked Questions
How do you add audio to a video?
Select the video, choose an audio file, pick whether to mix it under the original sound or replace that sound entirely, then click Add Music. If the video has no audio of its own, both choices do the same thing and your track simply becomes its soundtrack.
Does this mix the new audio with the original sound?
It can do either. Choose "Keep and mix" and the track sits underneath the original audio at whatever level you set, so speech and background stay audible. Choose "Replace" and the original is dropped and the new track takes its place.
What happens if the music is shorter than the video?
That is up to you, in either mode. Loop to fill repeats it until the video ends, which is what a music bed is expected to do. Play once suits anything that should not repeat - a voiceover, an intro sting - and leaves the rest of the video with only the original audio, or silent if you replaced it. A track that runs past the last frame is trimmed to fit, and the tool says which case applies before you start.
How loud should the background music be?
The 30% default is a reasonable bed: present, but not competing with speech. Drop to 15% where dialogue matters most, and raise it towards 75% when the music is the point and the original audio is just room tone. Peaks are clamped rather than allowed to wrap, so a loud setting compresses rather than distorting.
Does replacing the audio reduce the video quality?
No. The video stream is copied into the output untouched, so the picture is bit-for-bit identical to your source. Only the new audio is encoded, which is also why the process is much faster than a full re-encode.
Can I replace the audio on a YouTube video?
Only on a video file you have. YouTube does not let you swap the audio on something already published - you would replace the track here and upload the new version. Note that re-uploading starts the view count and URL over.
Which audio formats can I use?
MP3, WAV, M4A, AAC, FLAC, OGG and Opus all work, and you can also point it at another video file to take the audio from that. The track is re-encoded to suit whichever container you choose for the output.