Pokemon Showdown (or just Showdown) is a battle simulator, aimed at competitive players. You can play it in your web browser by following the link below.
Showdown allows you to build a team by typing Pokemon, moves, items, EVs, etc. into a teambuilder. It has separate matchmaking ladders for many battle formats. It is affiliated with Smogon as the home of its tiered battle formats (e.g. OU, UU) and other metagames (e.g. AG, Monotype). You can also play official formats like VGC and cartridge formats like Battle Stadium Singles.
Showdown has many features, such as chat rooms, replay sharing, tournaments, and chat commands. It is also open source. You can read Smogon's beginner's guide to Showdown for more information.
