# Replace Audio — Replace the audio in a video on Mac

Swap a video's soundtrack for another audio file. Part of OneMacTools, 151 private tools in one native Mac app (macOS 26 or later); category: Video. Runs on your Mac; nothing is uploaded.

Drop a video and an audio file. The picture is kept untouched and the new soundtrack is laid over it, stopping at whichever is shorter if you like.

Page: https://www.onemactools.com/tools/replace-audio · Download: https://www.onemactools.com/download · Pricing: https://www.onemactools.com/pricing

## How to use it
1. **Install FFmpeg once.** If needed, OneMacTools offers to install FFmpeg through Homebrew with one click.
2. **Drop a video and an audio file.** Add the video and the new soundtrack (MP3, M4A, WAV, FLAC and similar) together. You can add several videos and they all get the same audio.
3. **Decide where it ends.** Leave Stop at the shorter of the two on to end the result when either the video or the audio runs out.
4. **Click Replace.** The picture is copied untouched and the new soundtrack takes the place of the old one.
5. **Play it back.** Copies ending in “new audio” are saved in a new dated folder in Downloads › OneMacTools. Listen with the Preview (eye) button or open Show in Finder. Your video and audio files are unchanged.

## Options
- **Stop at the shorter of the two:** On by default. The result ends when the video or the audio ends, whichever comes first. Turn it off to keep the full length of the longer one.

## Tips
- Trim the music to length first with Trim Audio if you want it to start at a particular point, such as the chorus.
- If you want to keep the original sound and add music on top, this isn't the tool: Replace Audio swaps the soundtrack completely.
- Only the first audio file you drop is used. To try different songs, run the tool again with each one.
- For narration, record it with Record Audio, then clean it up with Clean Up Audio before adding it.
- Because the picture isn't re-encoded, the video keeps its exact quality.

## Questions
**How do I replace the audio in a video on a Mac?**
Drop the video and the new audio file onto Replace Audio together and click Replace. The picture is kept exactly as it was and the old sound is swapped out.

**How do I add music to a video?**
Drop the video and the song together and click Replace. The music becomes the soundtrack, ending with the video if Stop at the shorter of the two is on.

**What happens if the music is longer than the video?**
With Stop at the shorter of the two on, the music is cut off when the video ends. With it off, the file runs until the music ends.

**Can I keep the original sound and add music on top?**
No. Replace Audio swaps the soundtrack completely. Mix the two in an audio editor first if you need both.

**Can I give several videos the same soundtrack?**
Yes. Drop all the videos and one audio file; each video gets its own copy with the new sound.

**Why does it say “Add an audio file”?**
Replace Audio needs one audio file, such as an MP3, M4A or WAV, dropped along with the videos. A video can't be used as the soundtrack.