There is only one file type that uses the .UNIF extension:
UNIF ROM File
Game ROM used by the Nestopia emulator to play Nintendo Entertainment System (NES) video games; also used to play Famicom video games, which was the Japanese version of the NES.
The Universal NES Image Format (UNIF) is an alternative to the .NES format for storing NES and Famicom images. It was originally developed by Tennessee Carmel-Veilleux but then abandoned in 2008. Since 2011, the UNIF format has been maintained by the libunif project and.
NOTE: The UNIF file extension is not as common as the .UNF extension.
Updated: January 8, 2016