FLAC
audio/flac
Lossless audio for people who can hear the difference, or believe they can — FLAC compresses PCM to roughly half size with bit-perfect recovery, finally standardized as RFC 9639 after two decades as a de facto format. Send it for the native .flac container; FLAC streams muxed into Ogg are audio/ogg instead, and the pre-standard audio/x-flac label still leaks out of older tools. Every native FLAC stream opens with the fLaC marker, written into the spec itself.
Defined by RFC 9639 · IANA registration. Registry facts from the IANA media-types registry via mime-db.