OpenType

OpenType is a font format developed by Microsoft and Adobe in the 1990s as a successor to TrueType and PostScript Type 1. It is designed to unify scalable type technology and provide a robust, cross‑platform typography framework. An OpenType font can contain TrueType outlines or PostScript-based CFF (Compact Font Format) outlines within a single file, enabling a single font family to support a broad range of languages and features.

OpenType fonts typically use extensions such as .otf for PostScript/CFF outlines and .ttf for TrueType outlines, with .ttc used for collections containing multiple fonts. The format includes a rich set of tables that describe glyph shapes, metrics, and metadata, along with advanced layout capabilities. A key feature is the OpenType Layout framework, which uses GSUB (glyph substitution) and GPOS (glyph positioning) tables to enable ligatures, contextual alternates, small caps, oldstyle figures, diacritics positioning, and other typographic refinements.

Unicode-based character support allows OpenType fonts to cover extensive writing systems and modern multilingual typesetting. This interoperability makes OpenType the de facto standard for professional typography in desktop publishing, software interfaces, and the web. OpenType fonts are widely supported on major operating systems, including Windows, macOS, and Linux, and can be embedded in documents and web pages via standard font embedding mechanisms and CSS.

Overall, OpenType combines flexible outlines with a powerful typographic feature set, enabling sophisticated, script-driven typography across platforms.