A flash grenade, alternatively referred to as a flash bomb, was a non-lethal type of grenade that, upon activation, generated a brilliant flash of energy accompanied by a deafening sound. This combination was designed to disorient adversaries. While it produced a minor impact, it lacked the destructive power of thermal detonators, but it could temporarily disable droids. A specific model of this grenade had the ability to divide into multiple pieces, each detonating separately.
During 14 BBY, the Jedi Knight named Cal Kestis executed an infiltration of the Fortress Inquisitorius situated on Nur. His objective was to recover a holocron containing a directory of children sensitive to the Force. During this mission, Kestis encountered the Inquisitor known as the Second Sister, who deployed flash grenades in an attempt to disorient Kestis during their duel.
When Luke Skywalker embarked on a mission to Ben Kenobi's home alongside R2-D2, Boba Fett launched a surprise attack on them using a flash grenade. His intention was to seize Luke.