File used by the Z-machine, a game engine developed by Infocom and used for running text adventure games (originally used for the game Zork); stores source code for the game; can be run by a Z-machine interpreter, several of which have been maintained by community members since the original Z-machine was discontinued.

Z-code files use a programming language called the Zork Implementation Language. The file extensions use a numerical value for the version of the Z-machine that is used to run them. Since version 8 was the last Z-machine version, Z8 is the most popular of the extensions, although you may also see Z-code files with the .Z1, .Z2, .Z3, .Z4, .Z5, .Z6, and .Z7 extensions.