Font and typeface file extensions

Font file type can be defined as a set of characters, symbols or glyphs.

Fonts can be divided in three basic types: bitmap fonts, outline fonts and stroke fonts.

Bitmap fonts (raster fonts) consist of a series of dots or pixels representing the image of each glyph in each face and size. Bitmap fonts are faster and easier to use in computer code, but inflexible, and do require separate font for each size.

Outline fonts (vector fonts) use Bézier curves, drawing instructions and mathematical formulas to describe each glyph, which make the character outlines scalable to any size.

Stroke fonts use a series of specified lines and additional information to define the profile, or size and shape of the line in a specific face, which together describe the appearance of the glyph.

The most used font file formats are:

Adobe Type 1 (PFB file extension) and Type 3 fonts developed by Adobe for professional digital typesetting and desktop publishing. Type 1 and Type 3 fonts are outline fonts (vector fonts), which are using PostScript and cubic Bezier curves.

TrueType font (TTF file extension) is file format created by Apple, Inc as competition for Adobe Type 1 fonts. TrueType font is described by quadratic Bezier curves. It is a very popular font format, that is supported by many operating systems (Microsoft Windows, MAC OS X, Linux).

OpenType (OTF file extension) is a current standard font file format supported by modern operating systems that was designed by Microsoft and Adobe. OpentType fonts are based on Adobe Type 1 font and contain wide range of metadata and international/foreign character sets.