AAC audio in an MP4 container, which is what iTunes ripped to and what most podcast apps hand you. It sounds better than MP3 at the same bitrate. It's also the file that gets refused by car stereos and upload forms often enough to keep this converter busy.

Every conversion below runs in this page, on your own machine. Nothing is uploaded, there is no queue, and there is no account to make. Pick a target format, or just drop a M4A file above and choose afterwards.