Audio
Turn your AAC files into M4A in seconds. Everything happens in your browser: nothing is uploaded to any server.
Drag your files here
Or paste them with Ctrl+V. They never leave your device.
Without a container it holds no artwork or tags, and some programs prefer M4A. As M4A it sounds good at a small size and opens on iPhone, Android and Windows.
AAC is the lossy audio codec that replaced MP3; this file is “raw” AAC, without a container (ADTS).
Strengths: At the same size it sounds better than an MP3 and almost every device understands it.
Limits: Without a container it holds no artwork or tags, and some programs prefer M4A.
M4A is AAC audio in an MP4 container: the format of iTunes, iPhone voice memos and many podcasts.
Strengths: Good quality at a small size, with tags and artwork, and it opens on Apple, Android and Windows.
Limits: Some old players or editing programs only accept MP3 or WAV.
No. The AAC to M4A conversion runs entirely in your browser, with code downloaded from this site and executed on your device. You can check it in the Network tab of the developer tools or by going offline after the page loads.
A little, because M4A is lossy; at 192 kbps or more the difference is hard to hear.
Up to 2 GB on desktop and 500 MB on mobile (less on low-memory devices), and up to 12 hours of audio on desktop. If it is over, you are told before it starts.
Yes. Drop as many AAC files as you like: several are converted at the same time, depending on your processor cores, and when they finish you can download each M4A or all of them in a ZIP.