What is Crazyhouse?
Crazyhouse is chess in which no piece ever leaves the game. When you capture a piece, it changes colour and goes into your hand. On any turn you may either make a normal move or drop one piece from your hand onto any empty square, where it becomes an ordinary piece of your side.
A dropped piece may give check or even checkmate at once, so attacks come quickly and a king is never quite safe. A pawn may not be dropped on the first or last rank; dropped on its own second rank it may still step two squares. A pawn that promoted is remembered: if it is captured, it goes into the hand as a pawn, not as the piece it became.
Everything else is standard chess: the pieces move and capture as usual, and checkmate wins. You can play Crazyhouse online, against the computer, or with two people on one device. It doesn't combine with Chess960, Three-Check or material odds.
Rule changes
| Rule | Standard Chess | Crazyhouse |
|---|---|---|
| Captured pieces | Standard ChessLeave the game for good. | CrazyhouseChange colour and go into the capturer's hand, ready to be dropped. A captured promoted pawn goes into the hand as a pawn. |
| Drops | Standard ChessThere are no drops: every turn is a move of a piece on the board. | CrazyhouseInstead of moving, you may place a piece from your hand on any empty square. Drops may give check and checkmate, and a drop between your king and the checking piece is a way out of check. |
| Pawn drops | Standard ChessPawns only start on their second rank. | CrazyhouseA pawn may be dropped on any empty square except the first and last ranks, even on a file where you already have a pawn. Dropped on its second rank, it may still step two squares. |
| Castling | Standard ChessAllowed while the king and that rook have never moved. | CrazyhouseThe same. A rook dropped on its corner square later never brings the right back. |
| How to win | Standard ChessCheckmate the opponent's king. | CrazyhouseThe same, but a mate must also hold against every drop your opponent's hand allows. |
| Draws | Standard ChessStalemate, threefold repetition, the fifty-move rule and insufficient material. | CrazyhouseStalemate and threefold repetition, where both hands must also be the same. There is no fifty-move rule and no draw for lack of material, since captured pieces come back. A game still going after 600 moves in all is drawn, with a message saying so. |
History
Crazyhouse is the two-player, single-board form of bughouse, the four-player team game in which captured pieces pass to a partner. Bughouse became known in Western chess circles in the 1960s, but crazyhouse came into its own only in the 1990s, on the first internet chess servers, where two players anywhere could meet for a quick game.
The idea of bringing captured pieces back is much older. It is the defining rule of shogi, Japanese chess, which has played with drops for centuries. In 1972 the game designer Alex Randolph, who had moved to Japan and become an amateur dan-level shogi player, made a chess variant with shogi-style drops, an early relative of the game. Crazyhouse keeps fewer restrictions than shogi: a pawn may be dropped on a file that already has one of your pawns, and a pawn drop may give mate.
Today crazyhouse is offered on large chess sites with its own ratings and tournaments. The rules here follow the common online form.