.JAG File Extension
File Type 1Jagex Data File
What is a JAG file?
Game data file used by Jagex games such as Runescape, an MMORPG; can save various data, including images, sounds, and other game object data; stored in a proprietary format required by the game in order to load the game data.
File Type 2Atari Jaguar Game ROM
.JAG File Association 2
A JAG file contains a game ROM image created from an Atari Jaguar game. It stores an exact copy of the data dumped from an Atari Jaguar cartridge. JAG files are used to emulate Atari Jaguar games using an Atari Jaguar emulator, such as RetroArch, Phoenix, and MAME.
You most likely will only encounter a JAG file if you are looking to play an Atari Jaguar game on your computer or mobile device using an emulator. Atari Jaguar games may also be dumped to .J64 files.
NOTE: The Atari Jaguar was a 64-bit video game console released in 1993. It was a commercial failure and helped put Atari out of the home video game console market. However, the console has since gained a cult following, which has led to the rise in emulators supporting Atari Jaguar games.