Audio
Turn your AAC files into Opus 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 Opus it takes minimal space with very good quality, ideal for voice and the web.
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.
Opus is a modern, open codec that gives very good quality at a very small size, for both voice and music.
Strengths: It is the format of WhatsApp voice notes and video calls, and sounds good even at 96 kbps.
Limits: Some old, car or Apple players do not recognise it.
No. The AAC to Opus 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 Opus 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 Opus or all of them in a ZIP.