Replace the sound
Swap the original audio of a video for a song, a narration or any other audio file.
Add Audio to Video
Put a song or a voice-over on a video, right in your browser. Choose a video and an audio file: the music replaces the original sound, or is mixed with it at the level you choose, and loops if it is shorter than the video. The picture is copied as it is, so the quality stays the same and it only takes seconds. Nothing is ever uploaded.
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1Video
Drop a video here or click to choose
MP4, MOV, AVI, MKV, WebM, WMV, FLV, 3GP… · max 500 MB
2Audio
Drop an audio file here or click to choose
MP3, WAV, M4A, AAC, OGG, FLAC… · max 100 MB
3Options
Everything happens in your browser: your video and audio are never uploaded.
Main features
Add a soundtrack to any video in seconds, entirely on your device, without touching the picture.
Or mix it in
Keep the original sound at 25, 50 or 100 % and add the music on top, for background music under speech.
Any length
A short song repeats until the video ends, or leaves silence, as you prefer; a long one is cut at the end of the video.
The picture is not re-encoded
The video stream is copied byte for byte. Same resolution, same quality, and it takes seconds even for a large file.
Nothing is uploaded
FFmpeg runs inside your browser, so your video and audio never leave your computer or phone.
All common formats
Videos in MP4, MOV, M4V, AVI, MKV, WebM, WMV, FLV, 3GP and more; audio in MP3, WAV, M4A, AAC, OGG, FLAC and more. The result keeps the original container whenever possible.
Three clicks
Choose the video, choose the audio, click "Add audio to the video". Then download it.
Free, no account, no watermark
Make as many videos as you like. We only ask you to share the website if you find it useful.
Questions and answers
Is it really free?
Yes. There is no account, no limit on the number of videos and no watermark. The website is supported by ads.
Are my files uploaded to a server?
No. Everything is processed by your browser with FFmpeg compiled to WebAssembly. You can even disconnect from the internet once the page has loaded.
What if the audio and the video have different lengths?
The video always keeps its length. If the audio is longer, it is cut when the video ends. If it is shorter, you choose: repeat it from the beginning until the video ends, or leave silence after it.
Can I keep the original sound and add music on top?
Yes. Set "Original sound of the video" to 25, 50 or 100 %. The new audio is mixed with it at that level; 25 % is good for background music under a voice, 100 % for two sources of similar importance. If the video has no sound, the new audio simply replaces the silence.
Does the video lose quality?
The picture does not: the video stream is copied without re-encoding. Only the audio is encoded, as AAC at 192 kbps by default (or the codec the container expects), which keeps it indistinguishable from the source for normal listening.
Which formats are supported?
Videos: MP4, M4V, MOV, AVI, MKV, WebM, WMV, ASF, FLV, MPG, MPEG, VOB, TS, 3GP, OGV and more. Audio: MP3, WAV, M4A, AAC, OGG, OPUS, FLAC, WMA, AIFF and more. The output keeps the video's container and stream; the audio is encoded with the codec that container expects (AAC for MP4/MOV/MKV, Opus for WebM, MP3 for AVI…). For the few containers that cannot be written this way, the tool falls back to MP4.