Chess960 (Fischer random): rules, setup and how it differs

The idea was proposed in 1996 by Bobby Fischer, the eleventh world champion. What irritated him was that professional games had increasingly become a memory exercise: the first fifteen or twenty moves were played from preparation and the real contest started only afterwards. His fix returned spontaneity without breaking the game: the same board, the same 32 pieces and all the same rules, but each game starting from one of many randomized setups.

There are exactly 960 such setups - hence the other name. The classical position is one of them: with a probability of one in 960 the generator produces ordinary chess. In the other 959 cases the knights, bishops, queen and king stand elsewhere on the back rank, and the familiar openings simply cannot arise.

Fischer set three constraints, so that any random position stays playable and symmetrical:

• The bishops stand on opposite-coloured squares. One bishop is always on a light square and the other on a dark one, exactly as in classical chess.
• The king stands between the two rooks. This is what makes both castling directions technically possible from any starting position.
• Black mirrors White. If White's first rank is BBNRKRNQ, Black's eighth rank is the same. The game starts symmetrically and neither side gains an edge from the arrangement.

The pawns stand on their usual squares in all 960 variants - only the back rank changes. Each position carries a number from 0 to 959, and classical chess is number 518.

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Compare it with the classical setup - the board and the pawns are identical, only the order of the pieces differs.

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The one genuine technicality. The king and rooks start on arbitrary squares, so the familiar picture - the king steps two squares, the rook jumps over - does not apply. The principle is different and simple: after castling, the king and rook end up on exactly the same squares as in classical chess.

• Kingside castling. The king finishes on g1 (g8 for Black) and the rook on f1 (f8), regardless of where either started.
• Queenside castling. The king finishes on c1 (c8) and the rook on d1 (d8).

The conditions are the ones you know: neither the king nor that rook has moved, no other piece stands between them, the king is not in check and does not pass through an attacked square. Sometimes the king and rook already stand almost on their destination squares - the castling move then looks like a shift of one square, or like the two simply swapping places. That is normal and counts as a full move.

At the level of the rules the differences are small: the starting position and the castling logic. Everything else - how the pieces move, capture, check, mate, stalemate, promotion, en passant, the time controls - is identical - the rules of chess.

The difference in feel, though, is enormous. In classical chess the first moves are almost always theory, worked out to move fifteen and beyond. In Chess960 that does not exist: even a strong grandmaster sees a new position and thinks for themselves from move one. It narrows the gap between a newcomer and an experienced player in the opening, and professionals value it for the same reason - it is chess without preparation.

There are drawbacks. Some positions look strange: a queen in the corner, a bishop beside the king, knights in the centre. That takes getting used to. And systematic opening study, the way it works in classical chess, is simply not available - there is nothing to prepare.

A random position is needed before every game. There are several ways to get one:

• Lichess - free, with a dedicated Chess960 mode. Create a game, choose the variant, and the server picks a random starting position - playing online.
• Chess.com - a Chess960 mode with its own separate rating, and a larger pool of opponents.
• Over the board with friends. Use any generator for a number from 0 to 959 and set the pieces up by hand.

It is also a genuinely useful device for an organizer: a randomized start devalues opening knowledge and narrows the gap in a mixed field, without anybody being visibly given odds - levelling a mixed field.

And if you are still finding your way around the ordinary starting position, begin with setting up the board - which piece stands where, and why the queen takes her own colour.

• Chess960 is chess with 960 possible randomized starting positions, one of which is the classical one.
• The generation rules: bishops on opposite colours, the king between the rooks, Black mirroring White.
• Castling brings the king and rook to the same squares as in classical chess: g1 and f1, or c1 and d1.
• Every other rule - moves, check, mate, promotion - is unchanged.
• Play it on Lichess or Chess.com, or set a numbered position up by hand over the board.