Game file used by the game engine Z-machine, which was used for running text adventure games in the late 1970s and 80s; commonly run presently by a Z-machine interpreter, several of which have been maintained by community members since the Z-machine was discontinued; contains source code for the games and can hold up to 256K.

Z-code files use a programming language called the Zork Implementation Language (Zork was Infocom's first game). The file extensions use a numerical value for the version of the Z-machine that is used to run them. Examples include the .Z1, .Z2, .Z3, .Z4, .Z6, .Z7, and .Z8 extensions. NOTE: Z5 and Z8 files are the most popular versions of the 8 different Z-code file extensions.