Photon Geyser compares the user's Attack and Special Attack stats, dealing damage to the target using the higher stat. If the user's Attack is greater than its Special Attack, the move will be a physical move; if its Special Attack is equal to or greater than its Attack, it will remain a special move. During the execution of Photon Geyser, all ignorable Abilities (Abilities that could affect the success or damage of a move) are ignored, except when Photon Geyser is called by another move rather than directly used.
For determining which stat is higher, stat stages are taken into account; however, it does not consider the effects of held items (such as a Choice Band) or Abilities (such as Huge Power) that do not use stat stages. If the user's Attack is higher, Photon Geyser becomes a physical move in all aspects: the move's damage is affected by Reflect (but not Light Screen), it will activate Counter and Shell Trap (but not Mirror Coat), and it triggers the Kee Berry (but not the Maranga Berry). Otherwise it is treated as a special move in all of these cases.
Photon Geyser does not exist in the game data of Pokémon Sun and Moon. As a result, a Pokémon knowing Photon Geyser cannot be traded from Pokémon Ultra Sun and Ultra Moon to Sun and Moon, and if a Pokémon in Pokémon Bank knows the move it cannot be withdrawn in Pokémon Sun and Moon. In order to be transferred to Pokémon Sun and Moon, the Pokémon must forget Photon Geyser.