OpenTypefonts

OpenType fonts are a cross-platform font file format jointly developed by Microsoft and Adobe in the mid-1990s to unify scalable typography across systems. The OpenType specification wraps either TrueType or PostScript-based outlines inside a single file, enabling broad compatibility and a rich set of typographic features. An OpenType font may contain TrueType outlines stored in the glyf and loca tables or Compact Font Format (CFF) outlines stored in the CFF table, with the OpenType container providing common metadata and layout information.

A typical OpenType font includes a set of tables that describe the glyph shapes, metrics, and how text should be arranged. Core tables include cmap for mapping characters to glyphs, name for metadata, and head/hhea for metrics. For advanced typography, OpenType defines layout tables such as GSUB (glyph substitution) and GPOS (glyph positioning), enabling features like discretionary ligatures, contextual alternates, kerning, ordinal figures, and language-specific rules. OpenType fonts support Unicode and thus broad script coverage, making them suitable for many languages and writing systems.

OpenType rapidly became the de facto standard on Windows and macOS and enjoys wide support from font vendors and applications. The format preserves compatibility between older font data and newer enhancements while providing a flexible foundation for growth and tooling.

Extensions and variations have expanded OpenType beyond a single static font file. OpenType Font Variations (variable fonts) introduce the fvar table to allow a single font file to encode multiple design instances along axes such as weight or width. Other extensions include color and graphic capabilities via COLR/CPAL and OpenType-SVG, enabling colored glyphs and richer visual typography.