What happens when you convert MP3 to AAC
- The audio is decoded and written as AAC at 192 kbps in an ADTS stream.
- Going from one lossy format to another adds a small generation loss. Choose a bitrate at least as high as the source to keep it inaudible.
How to convert MP3 to AAC online
- Press "Choose MP3 files" and select one or more files, or drag them onto the box. You can add files of any size your device can hold in memory.
- Adjust the settings if you need to: the bitrate controls quality and size. The defaults suit most people.
- Press "Convert to AAC". The first audio or video conversion downloads the converter engine, about 32 MB, which your browser then keeps for next time.
- Save each AAC with its download button. Close the tab and every trace of the files is gone from memory.
Why convert MP3 to AAC?
MP3 files usually come from music libraries, podcasts and anything that has to play everywhere. People convert them to AAC because raw AAC streams are what some broadcasters, podcast tools and hardware players ask for.
In short, MP3 is good at what it was made for, and AAC is the more practical choice when the file has to play on another device or app. MP3 plays in every browser, phone, car stereo and media player, while AAC plays in all current browsers and on Apple and Android devices.
How to convert MP3 to AAC on Windows, Mac, iPhone and Android
On Windows
Open this page in Chrome, Edge or Firefox, drag your MP3 files in from File Explorer, and press Convert. Each AAC is saved to your Downloads folder. If you prefer a desktop program, VLC can also convert MP3 to AAC: choose Media, then Convert / Save.
On a Mac
Safari, Chrome and Firefox all work. Drag the MP3 files from Finder onto the drop zone and the AAC files land in Downloads.
On iPhone and iPad
Open the page in Safari and tap Choose MP3 files. You can pick from Photos or from the Files app. The converted AAC appears in Files, in the Downloads folder.
On Android
Open the page in Chrome, tap Choose MP3 files and pick them from Files or your gallery. The AAC is saved to the Download folder, where any file manager can find it. Keep the screen on while a long video converts, because Android may pause a tab in the background.
Best settings for MP3 to AAC
AAC is a lossy format, so the bitrate decides both the sound quality and the file size. Size grows in a straight line with bitrate: double the bitrate and the file doubles.
| Bitrate | Size per minute | Good for |
|---|---|---|
| 320 kbps | about 2.4 MB | the highest quality, for music you will keep |
| 256 kbps | about 1.9 MB | excellent music quality |
| 192 kbps | about 1.4 MB | the default: transparent for most listeners |
| 128 kbps | about 1.0 MB | good for music on the go and for podcasts |
| 96 kbps | about 0.7 MB | speech and audiobooks |
| 64 kbps | about 0.5 MB | voice notes and spoken word only |
The MP3 was already compressed, so pick a bitrate at least as high as the original. Going higher does not add quality back, it only makes the file bigger.
MP3 vs AAC: the differences
| MP3 | AAC | |
|---|---|---|
| Full name | MPEG-1 Audio Layer III | Advanced Audio Coding |
| Type | audio | audio |
| Created by | the Fraunhofer Institute | the Moving Picture Experts Group |
| First released | 1993 | 1997 |
| Compression | Lossy | Lossy |
| Usually contains | MP3 audio, typically 128 to 320 kbps | AAC audio in a raw ADTS stream |
| In a browser | plays in every browser, phone, car stereo and media player | plays in all current browsers and on Apple and Android devices |
| Common uses | music libraries, podcasts and anything that has to play everywhere | iTunes and Apple Music, YouTube audio and streaming |
| MIME type | audio/mpeg | audio/aac |
About MP3 and AAC files
What is an MP3 file?
MP3 is the most widely supported audio format there is, which is its whole appeal. At 320 kbps most listeners cannot tell it from the original; at 128 kbps cymbals and applause start to smear.
What is an AAC file?
AAC was designed as the successor to MP3 and sounds better at the same bitrate, especially below 128 kbps. A bare .aac file is a raw stream with no chapters or cover art; the same audio in a container is usually called M4A.
MP3 to AAC not working? Common problems
- The conversion is slow. Audio and container changes take seconds, but re-encoding video runs on your own processor. Lower the resolution to 720p, close other tabs, and keep the device plugged in.
- The tab stops or reloads on a very large file. Browsers limit how much memory one tab can use, around 2 GB and less on phones. Split long recordings or convert them on a computer.
- Song titles are missing. Tags such as title and artist are copied when AAC can store them, but cover art is not carried over.
Convert MP3 to AAC with ffmpeg
This converter runs ffmpeg inside your browser. If you would rather use the ffmpeg command line on your own computer, this command produces an equivalent AAC with the same kind of settings:
ffmpeg -i input.mp3 -vn -c:a aac -b:a 192k -f adts output.aacReplace input.mp3 with the name of your file. For a whole folder of MP3 files, run the command in a loop, or drop them all on the converter above, which processes them one after another.
MP3 to AAC converter FAQ
Will I lose quality converting MP3 to AAC?
A little. Both formats are lossy, so re-encoding compounds the loss slightly. Keep the default bitrate or higher and the difference is rarely noticeable.
Why is the AAC a different size from the MP3?
It depends on the settings. At the defaults, the AAC usually comes out close in size to the MP3; lower the bitrate for a smaller file.
Are my MP3 files uploaded anywhere?
No. The conversion runs inside this browser tab using ffmpeg compiled to WebAssembly, so your files stay on your device. You can disconnect from the internet after the page and converter engine have loaded and it still works.
Can I convert several MP3 files to AAC at once?
Yes. Select or drop as many files as you like; they are converted one after another and each gets its own download button.
How do I open an AAC file?
AAC plays in all current browsers and on Apple and Android devices. AAC is common for iTunes and Apple Music, YouTube audio and streaming.
Is this MP3 to AAC converter free?
Yes. There is no sign-up, no watermark and no limit on how many files you convert. The site is paid for by advertising, and because conversions run on your device there is no server cost per file.
Can I convert MP3 to AAC on my phone?
Yes. The converter works in Safari on iPhone and iPad and in Chrome on Android. Converted files are saved to the Downloads folder.