The best chess server is free for all, open source, and without ads!
Play chess with a friend, with a random player or with the computer.
It is free. You don't have to register. There are no ads.
Lichess lets you focus on the game by removing all clutter.
Two-player games between humans
Single-player (versus the artificial intelligence, Crafty)
Time controls for chess clocks, including Fischer time settings
User-defined restriction of who can join games, based on player rating
Chess960, also known as Fischer Random, chess variant
Castling, en passant, and pawn promotion and under-promotion
Detection of check, checkmate, and stalemate
Threefold repetition draw recording (must be claimed by player)
Visual move validation while choosing destination squares
Game replay and analysis
Per-game export in portable game notation
Database export of information about all games played by a given person as comma-separated values (CSV)
Translated to fifty languages
Works in any Internet browser (except IE6/IE7), with no Flash and no plugins.