groff is GNU Project's free replacement for troff and nroff. unroff is an extensible replacement of troff written in Scheme Heirloom troff is based on troff from OpenSolaris. It includes support for OpenType fonts, improved support for Type 1 fonts, support for Unicode, a new paragraph formatting algorithm, and a groff compatibility mode. mandoc is a specialised compiler/formatter only for the man and mdoc macro packages.