Prestige

Prestige (Japanese:  Prestige) was the fundamental basis for the system used in Pokémon GO from the game's launch on July 6, 2016 until June 22, 2017. This system is now defunct, being replaced by a motivation-based system.

Gyms
In the prestige system, any Gym that was under the control of a team had a level, which was determined by its Prestige. The Gym's level determined the number of defending Pokémon that could be placed in it. If a Gym's level fell below the number of defending Pokémon, the Pokémon with the lowest was ejected from the Gym and returned to its owner. If a Gym's level was higher than the number of Pokémon currently stationed there, a Trainer on the same team as the Gym could add an additional Pokémon.

Gyms begin as neutral with 0 Prestige and available to be claimed by any team. Stationing a Pokémon in a neutral Gym would claim that Gym for that player's team. When a Gym is claimed for a team, it transform to display the colors of the team currently holding it. Stationing a Pokémon in a Gym increased the Gym's Prestige by 2000, so a newly claimed Gym would increase to level 2, allowing a second Pokémon to be stationed there.

Players from the same team could train at a Gym to increase its Prestige, up to a maximum of 50000. The Gym gained Prestige for every Pokémon a player that trained at the Gym defeated, with additional prestige gained if the attacking Pokémon's CP was lower than the defending Pokémon's CP.

Players from an opposing team could challenge the Gym to decrease its Prestige. The Gym lost Prestige for every Pokémon a challenger defeated, with a bonus Prestige loss if the challenger defeated all of the Gym's defending Pokémon. A Gym lost approximately 1 level for every victory against all of its defenders, so it would take multiple victories in order to claim a Gym if it has a high level.

Though a Gym with 50000 Prestige would still have its Prestige increased by 2000 if a new Pokémon was added to it, the Gym's Prestige would be automatically lowered back to 50000 if another player battled or trained there.

Once a Gym's Prestige reached 0, it became neutral and not controlled by any team, available to be claimed by any team.

Defenders
A Gym could house multiple defenders, the maximum number of defenders being equal to its level. A player in range of a Gym on the same team as it could add one of their Pokémon to the Gym, provided there was room. A player could only have one of their Pokémon in each Gym.

Only Pokémon with full HP could be deposited in a Gym as a defender. A Pokémon placed in a Gym could not be removed until it was removed due to the Gym's Prestige falling too low, at which point the Pokémon will return to its owner's collection, but with 0 HP. While in a Gym, Pokémon could not be evolved, Powered Up, or used for battle at another Gym.

Levels
The amount of Prestige required to level up a Gym increased as the Gym's level increased.

Battling at a Gym
Players can train at friendly Gyms to increase the Gym's Prestige, or challenge opposing Gyms to decrease its Prestige. The mechanics of both kinds of battle are similar, with the player battling the Gym's Pokémon, which are AI controlled. In both cases, defeating Pokémon at Gyms will yield a small reward of XP.

When challenging a rival Gym, the player selected a team of six of their own Pokémon to battle against the defending Pokémon. If multiple players challenged a Gym at the same time, they would automatically collaborate, with the Gym's defenders' HP decreasing for all challengers at once. An icon with a number would appear on the left-hand side of the screen indicating the number of players currently challenging that Gym. If all of a challenger's Pokémon fainted or time ran out, that player lost the Gym battle. If all of the Gym's defending Pokémon fainted, the remaining challengers won the Gym battle. After a challenger's battle ended, that challenger received XP for each defending Pokémon defeated and the Gym lost Prestige, with an extra decrease if all of the Gym's defenders are defeated.

From October 12, 2016 until the motivation system, when training at a friendly Gym, the player selected a team of six of their own Pokémon to battle against the defending Pokémon (with their CP lowered based on how strong the training player is). Prior to October 12, 2016, players training at a Gym could only bring one Pokémon and the Pokémon used their regular CP. After the battle ended, the training player received XP for each defending Pokémon defeated and the Gym received a Prestige increase, with an extra increase if all of the Gym's defenders are defeated.

Defender bonus
Every 21 hours, players could claim the Defender bonus from the Shop menu using the Shield icon in the top right corner. Upon claiming it, the player received 500 and 10 PokéCoins for every Gym they held at the time of the claim, up to a maximum of 10 Gyms. Until the player claims their bonus, the timer would not reset.