Convert MP4 to AAC
We turn MP4 into AAC right in your browser — the file never goes to a server.
What you will lose
Nothing important: the target format does everything the source does.
How they differ
| MP4 | AAC | |
|---|---|---|
| Lossless | no | no |
| Lossy | yes | yes |
| Multichannel | yes | yes |
| Tags | yes | yes |
| Released | 2001 | 1997 |
| Author | MPEG | MPEG |
MP4
Good at
- Plays on everything: TVs, car stereos, phones a decade old
- Carries several audio tracks, subtitles and chapters in one file
- Streams well: playback starts before the file has finished loading
Awkward about
- Anything can be inside — the extension does not tell you if it will play
- The audio is almost always lossy, so it is not a master copy
- Editing without re-encoding is close to impossible in this container
Use it when
- The video is being sent or published and has to open for everyone
- Footage from a phone that people will simply watch
- One audio track is all you need
AAC
Good at
- Noticeably better than MP3 at the same size
- The native format for Apple gear and most phones
- Handles multichannel audio and tags
Awkward about
- Older devices and car stereos may refuse it
- Lossy — the original cannot be recovered from it
- Encumbered by patents, unlike Opus
Use it when
- Listening on a phone without wasting quality
- A voice memo, or a track pulled out of a video
- You want a balance between size and sound
Common questions
- Does the file get uploaded to a server?
- Yes, this pair needs the server: browsers cannot encode that format. The file and the result are deleted within a couple of hours and never shared.
- Will surround sound survive?
- Yes, AAC carries more than two channels — 5.1 stays 5.1.
- Can I get the original quality back afterwards?
- No. AAC is lossy, and the discarded detail cannot be recovered. Keep the original if you may still need it.
- How many files, and how large?
- Up to 5 files at a time, 500 MB each. No sign-up, no watermarks.