Audio
Turn your MP3 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.
It loses some quality with each re-encode and, at the same size, sounds worse than AAC or Opus. As M4A it sounds good at a small size and opens on iPhone, Android and Windows.
MP3 compresses sound lossily, removing what the ear barely notices, so a song takes just a few megabytes.
Strengths: Any phone, car, speaker, player or program plays it, however old.
Limits: It loses some quality with each re-encode and, at the same size, sounds worse than AAC or Opus.
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 MP3 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 MP3 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.