The KGS Go Server, known until 2006 as the Kiseido Go Server, is a game server first developed in 1999 and established in 2000 for people to play Go. The system was developed by William M. Shubert and its code is now written entirely in Java. A list of the top 100 players, sorted by KGS calculated rank, is regularly updated and maintained.
International tournament games and national championship games are relayed on this server. Monthly Computer Go tournaments are held in the Computer Go room on KGS.
The KGS Go Server is distinguished by a kibitz culture. Kibitzes are common and popular in high-level games, and may include off-topic discussions though this is discouraged by the administrators. The two players cannot see kibitzers' comments until after the game.
There are several client programs to connect to KGS. CGoban 3 is for normal use, on any system that supports Java. It supports 30 different languages, and can also be used as an Smart Game Format (SGF) file editor and viewer. A java applet version of CGoban3 is available, but lacks the ability to save files to the users computer and cannot be used as an SGF file editor/viewer. kgsGtp is another java program, for use by Go-playing programs. KGS Client for Android is for mobile phones that use the Android operating system; it supports several languages, but not as many as CGoban 3.
KGS allows games on any size board up to 37x37, including the 19x19, 13x13 & 9x9 boards. Games can be rated, free, teaching or pair games.
The players on the KGS are rated, using levels from 30 kyu to 9 dan, according to their results in 19x19 games.