Font collection
font/collection
A TrueType or OpenType collection: several related fonts in one file, sharing glyph tables to save space. It exists mostly for CJK families, where regional variants share thousands of identical glyphs, and for system font bundles like the weights of a family shipped together. Registered by RFC 8081 along with the rest of the font tree. You will rarely serve one over HTTP — collections live in operating system font directories, and the web equivalent is separate WOFF2 files per face.
Magic bytes
74 74 63 66 · "ttcf" · offset 0
Per Microsoft OpenType spec — font collections · test a file against it.
Defined by RFC 8081 · IANA registration. Registry facts from the IANA media-types registry via mime-db.