The FSP file extension was used by a small freeware program called Fsplit. It allows you to split a large file into several smaller ones. This makes it possible to store large files on several smaller media. The size or number of files after division is determined by the user.

FSP files are used to store some of the data from a file split by Fsplit. The principal names of such parts were assigned sequentially. Nowadays, when large media is available to users, this tool is rarely used and the FSP format is considered obsolete.