How do I add audio to a video?

Drop the video into the box, choose the audio file under Audio file to add, pick whether to replace or mix and press Add audio. The tool makes one MP4 with the new sound, and you download it.

How do I add background music and keep the original sound?

Choose Keep it and mix the new audio in, and set the volume of the music to 30% or 50% so the speech stays clear. The video's own sound and the music then play together.

What if the audio is longer than the video?

The result is never longer than the video, so the end of the audio is cut off when the video ends. The page tells you by how much once you choose the audio file.

What if the audio is shorter than the video?

The audio plays through once and then stops, and the rest of the video has no new sound. To fill a longer video, join the music to itself first or use a longer track.

Which audio formats can I add?

MP3, WAV, M4A, AAC, OGG, Opus and FLAC, and the sound of most video files. The sound is saved in the result as AAC at 192 kbps.

Does adding audio reduce the picture quality?

Not for MP4, MOV and M4V videos, whose picture is copied exactly. Other video types, such as WebM, are re-encoded to MP4 at a high quality setting so the result plays everywhere.

Can I add a voiceover I record myself?

Yes. Record it with the voice recorder, download it, and choose it here as the audio file. Set the video's own sound to be replaced for a clean voiceover.

Is my video uploaded, and is it free?

Nothing is uploaded. Both files are processed in your browser with a WebAssembly build of FFmpeg, and only the engine is downloaded the first time. It is free, with no watermark, no account and no limit.

Add Audio to Video — Add Music or Voiceover, Free

Add audio to a video online: put music or a voiceover on a clip, replace its sound or mix it in at a lower volume. Free, no upload, in your browser.

Last updated: 8 October 2026

Drop a file here or click to browseMP4, MOV, WebM, MKV, AVI — the video to put sound on🔒 Processed on your device — never uploaded

Audio file to add(required)

MP3, WAV, M4A, AAC, OGG, Opus or FLAC. It starts when the video starts.

What to do with the video's own sound

If the video has no sound, the new audio simply becomes its sound.

Volume of the new audio

Was this tool useful?

Use the tool above and you can rate it here.

Put your own sound on a video

Choose a video and an audio file, decide whether the new sound replaces the video's own or is mixed in with it, set the volume, and download one MP4 with both together. Music for a silent clip, a voiceover for a screen recording or a better soundtrack for a holiday video all work the same way. Everything happens in your browser and nothing is uploaded.

Replace the sound or mix it in

Replace throws away the video's own sound and uses only the new audio, which is what you want for music over a silent clip or a clean voiceover. Mix keeps the video's sound and plays the new audio together with it, which suits quiet background music under speech. If the video has no sound at all, the new audio simply becomes its sound whichever you choose.

How long the result runs

The finished video is never longer than the original. If the audio is longer, its end is cut off where the video ends; if it is shorter, it finishes and the rest of the video is silent. After you choose the audio file the page tells you which of these will happen, and by how much. To use only part of a long track, cut it first with the MP3 cutter.

Choosing the volume

100% uses the audio as it is, and 70%, 50% and 30% turn it down. Music under speech usually sits best at 30% to 50% so voices stay clear, while music alone on a silent clip can stay at 100%. If a track is too quiet to begin with, raise it first with increase video volume.

What happens to the file

For MP4, MOV and M4V videos the picture is copied across without re-encoding, which is fast and loses nothing. Other types of video, such as WebM or MKV, are re-encoded to MP4 so they fit. The sound is saved as AAC at 192 kbps. Need to record a narration first? The voice recorder makes one in your browser, and remove audio from video strips a sound you no longer want.

Frequently asked questions

How do I add audio to a video?: Drop the video into the box, choose the audio file under Audio file to add, pick whether to replace or mix and press Add audio. The tool makes one MP4 with the new sound, and you download it.
How do I add background music and keep the original sound?: Choose Keep it and mix the new audio in, and set the volume of the music to 30% or 50% so the speech stays clear. The video's own sound and the music then play together.
What if the audio is longer than the video?: The result is never longer than the video, so the end of the audio is cut off when the video ends. The page tells you by how much once you choose the audio file.
What if the audio is shorter than the video?: The audio plays through once and then stops, and the rest of the video has no new sound. To fill a longer video, join the music to itself first or use a longer track.
Which audio formats can I add?: MP3, WAV, M4A, AAC, OGG, Opus and FLAC, and the sound of most video files. The sound is saved in the result as AAC at 192 kbps.
Does adding audio reduce the picture quality?: Not for MP4, MOV and M4V videos, whose picture is copied exactly. Other video types, such as WebM, are re-encoded to MP4 at a high quality setting so the result plays everywhere.
Can I add a voiceover I record myself?: Yes. Record it with the voice recorder, download it, and choose it here as the audio file. Set the video's own sound to be replaced for a clean voiceover.
Is my video uploaded, and is it free?: Nothing is uploaded. Both files are processed in your browser with a WebAssembly build of FFmpeg, and only the engine is downloaded the first time. It is free, with no watermark, no account and no limit.