audio/mpeg

The type that carried the podcast era: MPEG audio layers I through III, which in practice means MP3. Send it for .mp3 files and streams; the widespread audio/mp3 label is a folk invention no registry defines, and audio/mpeg is what content negotiation expects. Identification is two-faced — files tagged with metadata open with ID3, while raw streams begin mid-frame with a sync pattern like ff fb, so a missing ID3 header does not mean a mislabeled file.

.mp3 dominates; the .mpga and .mp2 extensions survive from the layer I/II days.

Defined by RFC 3003 · IANA registration. Registry facts from the IANA media-types registry via mime-db.