Add Audio to Video
Add a music or voice-over track to a video, replacing the original sound or mixing the two together.
Add one video and one audio file. The result keeps the video's length.
Add audio
MP3, WAV, M4A, OGG, FLAC, OPUS — or a video to pull audio from.
Choose an output
Add a music or voice-over track to a video, replacing the original sound or mixing the two together.
Fine-tune
Optional — sensible defaults are already set.
About Add Audio to Video
Put a music track or voice-over onto a video. You can replace the original soundtrack entirely or mix the new audio with it, set the new audio's volume from 0 to 200 percent, and loop short music so it covers the whole clip. The output is an MP4 that keeps the video's length.
When it helps
- Adding background music to a phone video or slideshow before posting
- Replacing noisy wind or crowd sound with a clean voice-over
- Laying narration over a screen recording while keeping the original system sounds
- Dubbing a translated voice track onto a clip
Tips
- Use 'Mix' with the new audio around 20 to 40 percent for background music under speech; use 'Replace' for full voice-overs.
- If the music is shorter than the video, keep looping on; turn it off if you want silence after the track ends.
- If the video is already H.264, the picture is copied without re-encoding, so quality is untouched and processing is faster.
- Large files are slow to process in WebAssembly and must stay under 2 GB.
Good to know
Quick answers about add audio to video in your browser.
Choose 'Mix with new audio' and lower the new audio volume until the original voices are still clear, usually between 20 and 50 percent.
The output always matches the video's length, so extra audio is cut off at the end of the video.
Yes. There is no sign-up, no watermark and no limit on how many files you process.
No. Files are read and processed locally in your browser, so they never leave your device.
Runs in WebAssembly: large files are slow and must stay under 2GB.
Related tools
Part of the Audio Effects & Tools collection.