How to Add Music or a Voiceover to a Video (Free, in Your Browser)

Step by step

1. Open the toolGo to Add Audio to Video — it runs in your browser, with no install or account.
2. Add your videoDrop in an MP4 or MOV clip (H.264 or H.265). This is the picture that will be kept exactly as-is.
3. Add your audioDrop in the music or voiceover — MP3, WAV, M4A, or OGG. It will become the video’s new soundtrack.
4. Combine and downloadClick Combine into one video, preview the result, and download the MP4. Everything happens on your device.

No re-encoding, no quality loss

Most tools re-encode the whole video when you add audio, which is slow and quietly degrades the picture. This one stream-copies the video track — the exact same frames go straight into the new file — and only encodes the audio (to AAC). The combine is fast even for long clips, and the video looks identical to the original.

How the audio is handled

The new audio replaces whatever sound the video had, so the result carries just your track. It is automatically trimmed to the video’s length, so the file ends when the video does — handy for setting a clip to a song without a long silent or musical tail. If your audio is shorter than the video, the remainder simply plays without sound.

Private, and what works best

It all runs locally with your browser’s built-in video codecs (WebCodecs), so your files never leave your device and there is no big engine to download. Use an MP4 or MOV video (H.264/H.265) and an MP3, WAV, M4A, or OGG audio file, in an up-to-date Chrome, Edge, or Safari. If the tool says your browser can’t encode audio, switch to one of those.