OpenType font

font/otf

Extensions

.otf

Compressible

yes

Status

IANA-registered

An OpenType font with PostScript CFF outlines — the OTTO signature is what separates a .otf from a .ttf, since both are the same sfnt container inside. That is the trap: the ttf/otf split describes the glyph outline format, not two different file structures, and an OpenType font with TrueType outlines is correctly served as font/ttf. Registered by RFC 8081 to replace labels like application/x-font-otf; on the web, convert to WOFF2 instead of serving raw font binaries.

Magic bytes

4f 54 54 4f · "OTTO" · offset 0

Per Microsoft OpenType spec — font file tables · test a file against it.

Defined by RFC 8081 · IANA registration. Registry facts from the IANA media-types registry via mime-db.

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