Pokémon Showdown

Pokémon Showdown is a self-described "battle simulator" that faithfully recreates the battle system of the Pokémon main RPG series, with particular emphasis on high-level competitive play. The game supports a range of pre-set battle formats and rulesets, including both popular fan-made rules and the rulesets used by officially-sanctioned Pokémon tournaments. Players may use either a randomly-selected team, or a team of their own design in order to battle other users and climb the leaderboards.

The game is sponsored by Smogon, an online community of competitive Pokémon players.