GD is a file extension native to GD Graphics Library, a graphics library used by programmers. GD Library is an open source software developed by Thomas Boutell.

GD is a graphics file used by GD Graphics Library. GD Library was written in C programming language, but it also supports other languages such as  PHP, Perl, OCaml, Tcl, Pascal, or REXX. It allows users to create GIF, JPEG, PNG, and BMP images.