1.N@e7+ Kh8 2.Bxg7# (@ notation)
1.N@e7+ Kh8 2.Bxg7# (@ notation)

Crazyhouse (also known as drop chess, mad chess, reinforcement chess, turnabout chess and schizo-chess) is a chess variant in which captured enemy pieces can be reintroduced, or dropped, into the game as one's own. The drop rule resembles that of shogi;[1] the two games are often compared though no evidence suggests the one developing from the other. Crazyhouse is similar to bughouse chess; however, a game of Crazyhouse involves only two players.


The rules of chess apply except for the addition of drops, as explained below.

Unlike in shogi, dropping a pawn on a file containing another pawn of the same color and dropping a pawn to deliver checkmate are both permissible.[3]


To extend the standard algebraic notation, a drop is notated by inserting an at sign between the piece type and the destination square. For example, N@d5 means "knight is dropped on d5."[2]


There is no standard FEN specification for Crazyhouse. Lichess uses an extended version of FEN, adding a 9th rank as a reserve. Here is an example of Lichess's FEN implementation:[4]

r2qk3/pp2bqR1/2p5/8/3Pn3/3BPpB1/PPPp1PPP/RK1R4/PNNNbpp b - - 89 45

In XBoard/Winboard's notation system, the reserve is given in square brackets following the board position:

r2qk3/pp2bqR1/2p5/8/3Pn3/3BPpB1/PPPp1PPP/RK1R4[PNNNbpp] b - - 89 45

In Chess.com's notation system, the reserve is located after the full-move number.

To keep track of which pieces are promoted, Lichess and XBoard/Winboard use "~" after the letter designation. Chess.com uses the coordinates of the pieces.[5][failed verification]

r2q1r1k/2p1ppb1/p2p2pp/3P1p2/B6B/2N2NPp/1PP2P1K/3Q3q w - - 0 26 NNBRpr h1


Crazyhouse has several related variants:

See also


  1. ^ "Decoder of Crazyhouse". Retrieved 18 December 2022.
  2. ^ a b "crazyhouse". FICS Help. Free Internet Chess Server. 2008-02-28. Archived from the original on 2014-04-16. Retrieved 2014-04-17.
  3. ^ a b c "crazyhouse". ICC Help. Internet Chess Club. Archived from the original on 2012-05-02. Retrieved 2014-04-17.
  4. ^ ""IM opperwezen vs LM JannLee in T6Q3tMva : Analysis board • lichess.org"". Lichess. Archived from the original on 2018-05-26. Retrieved 2018-05-26.
  5. ^ ""Chess: liviu78ro vs JannLeeCrazyhouse - 3367504566 - Chess.com"". Chess.com. Archived from the original on 2019-01-17. Retrieved 2019-01-17.
  6. ^ "Game rules (Loop Chess)". BrainKing. Retrieved 2014-04-17.
  7. ^ "Chessgi". ChessVariants.org. 2001-03-20. Archived from the original on 2014-03-27. Retrieved 2014-04-17.