Compressed file used to store, or "pack," files on Unix-based machines; incorporates a simple compression algorithm that is used to archive files and save disk space; can be decompressed on a Unix system by typing uncompress filename.z, where "filename.z" is the name of the file to decompress.

Z files have mostly been replaced by GNUzip compression, which creates .GZ files. Unix users can use the znew utility to recompress Z files to GZ files.