Font Collection MIME Type

What is font/collection?

font/collection identifies one binary file that packages multiple related font faces. The TrueType Collection and OpenType Font Collection structures can share identical tables among the included faces, which can save space when a family contains several styles with overlapping glyphs. The file may use TrueType, CFF, CFF2, or SVG outlines; “TrueType Collection” is a historic name for the collection structure, not a restriction to one outline technology.¹²

The most familiar suffix is .ttc. OpenType also uses .otc. The registered type is font/collection; it is distinct from font/ttf and font/otf, which usually identify one font resource.

How to identify a collection file

A collection begins with the four-byte tag ttcf, followed by a collection header that describes the version and the offsets of the member font directories. Individual faces then refer to their own table directories, and identical tables may be shared.²

The IANA registration for font/collection lists .ttc and describes the outline signatures found within its member fonts. The OpenType specification identifies the collection header as ttcf and also reserves .otc for collection files. File names are useful hints, but a font-aware validator should inspect the header and internal offsets before installing a downloaded font.¹²

Opening and using font collections

Font Book on macOS and the Fonts settings in Windows can install and inspect supported .ttc collections.³ CSS Fonts defines the collection format hint for use with @font-face; test collection loading and face selection in your target browser and operating system.⁴ RFC 8081 defines a fragment syntax that selects a member by its PostScript name; if no name is supplied or it does not match, the first member is selected.¹

When you need one face as a standalone file, use a font editor or collection-aware conversion utility to export that face as .ttf or .otf. Preserve the original collection when faces share tables. Renaming a collection does not extract or convert its faces.

Support in Poly

Poly shows the filename and ordinary file properties in search, and makes extracted font properties available in the file details. Its metadata includes the total face count, but its detailed style information and specimen represent only the first face. The rendered specimen supports visual similarity search. This means a collection with regular, bold, and italic members appears as one preview rather than a set of separately selectable previews. Font names and glyph metadata are not full-text search fields or filters.

The Poly agent can inspect that rendered specimen and its accompanying font summary. It cannot examine every glyph or font table in every member. If you need to verify a particular face, open the file in a font application or export that face before adding it to Poly.

History of the media type

The collection structure predates its MIME label. RFC 8081 registered font/collection in February 2017 as part of the new font top-level media type. It gives collections a distinct label from individual TrueType and OpenType fonts.¹

Security and licensing

Collections contain complex binary tables that are interpreted by font software. RFC 8081 warns that malformed or malicious fonts can consume excessive CPU or memory, and some hinting instructions are executed by the font renderer. Install collections only from sources you trust, and keep font software current.¹

The faces in a collection may have distinct names and licensing terms. Check the license for each face before embedding, converting, or redistributing the collection. The collection wrapper does not grant rights to its contents.