AACAdvanced Audio Coding
MP3’s successor, more efficient at the same bitrate. You find it in videos, online radio and M4A files.
- Compression
- Lossy
Convert AAC to MP3
Turn your AAC files into MP3 files in seconds. Conversion happens in your browser, so your files are never uploaded to a server.
- Files never uploaded
- Free, no sign-up
- No queue
AACFFF150802D7FFC21
MP34944330400000000
The first bytes of a file often reveal its real format.
or drop them here. You can also paste an image (Ctrl+V).
Free · No sign-up · No upload
Files
These sample files are generated on the page. Convert them to try it out, or add your own.
How to convert AAC to MP3
- 01
Add your AAC files
Click “Choose AAC files” or drop them on the page. You can add several at once.
- 02
Check the MP3 format
MP3 is already selected. Choose the bitrate, from 128 to 320 kbps.
- 03
Convert and download
Click “Convert”, then download your MP3 file. With several files, grab everything at once as a ZIP.
AAC to MP3: what to know
An .aac file holds a raw AAC stream, without the MP4 container of an M4A. You get one from some recording apps, by recording an online radio station, or by extracting a video’s sound without re-encoding it. The conversion decodes the stream and encodes it as a constant-bitrate, 44.1 kHz MP3, keeping mono or stereo. ID3 tags that a program placed at the start of the file are copied into the MP3.
At the same bitrate, AAC sounds better than MP3. To avoid losing quality along the way, aim one step above the source: 192 kbps for a 128 kbps AAC, 320 kbps for a 256 kbps AAC. HE-AAC radio streams, often at 48 or 64 kbps, gain nothing above 128 kbps: what the original encoding removed does not come back.
AAC vs MP3: what’s the difference?
MP3MPEG-1 Audio Layer III
The most universal audio format. Its compression shrinks files a lot while keeping good listening quality, and it plays on every device.
- Compression
- Lossy
AAC to MP3: frequently asked questions
What is the difference between an .aac file and an .m4a file?
The sound is the same, AAC, but the packaging differs. An .m4a stores that sound in an MP4 container, with a title, artwork and an exact duration. An .aac is a raw stream with no container, which some devices and apps handle poorly. Both convert to MP3 in exactly the same way.
Why does my .aac file show the wrong length or skip badly when I seek?
A raw AAC stream has no index: the player estimates the length from the first few seconds, which goes wrong when the bitrate varies, and seeking becomes approximate. The MP3 created here uses a constant bitrate, so its length can be calculated exactly and jumping around the file is precise again.
Are my AAC files uploaded to the internet?
No. The file is read and converted by your browser, on your device. Nothing is sent to a server, and nothing is kept after you close the page.
Does converting AAC to MP3 reduce quality?
MP3 is a lossy format. At the default bitrate (192 kbps) the difference is inaudible to most listeners; choose 320 kbps for the best quality.
How many AAC files can I convert?
As many as you like, for free and without signing up. Add them all, then download the results one by one or in a single ZIP. The maximum size depends on your device and browser, with a few caps that protect its memory (for example 20,000 files per archive or 5 million filled cells per workbook: see the home page FAQ); a file over one of them is not converted, and a message says so.
Does it work on iPhone and Android?
Formatomat is designed for recent browsers on computers, iPhone and Android, with no app to install. A conversion the browser cannot do (a format it cannot read or write) is refused with a message that says so.