.TTC

Introduction

A TrueType collection packs several TrueType or OpenType fonts into one file, so that they can share tables they have in common. It is used mostly for CJK fonts, where thousands of glyphs can be shared between, for example, a proportional and a fixed-width version of the same typeface, and for system fonts on Windows and macOS that come in several weights.

Collections of fonts with CFF outlines may use the extension .otc.

Structure

A collection is big-endian. It starts with a header: the tag ttcf, a version (1.0, or 2.0 which adds fields for a digital signature), the number of fonts and a 32-bit offset for each font. Each offset points to an ordinary offset table and table directory, the same as at the start of a single TrueType font. The table records of different fonts may point to the same table data, which is how the fonts share glyphs.

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