WOFF2
font/woff2
The only font format the modern web needs: WOFF's successor, swapping zlib for Brotli plus font-specific preprocessing for roughly 30 percent smaller files. Every current browser supports it, so a single woff2 source in @font-face replaces the old four-format stack of eot, ttf, woff, and svg fonts. It is already compressed — configure your server not to gzip or brotli it again, and serve it as font/woff2, not the legacy application/font-woff2.
Magic bytes
77 4f 46 32 · "wOF2" · offset 0
Per W3C WOFF File Format 2.0 — WOFF2 header · test a file against it.
Defined by RFC 8081 · IANA registration. Registry facts from the IANA media-types registry via mime-db.