Chess960 position generator

Every position, one page each

All 960 arrangements have a page of their own with its FEN, the squares the king and rooks castle from, and what is distinctive about it. Start with position 518, which is the ordinary chess array, or jump to 0, 240, 480, 720 or 959. Any number from 0 to 959 works as /generator/<number>, and /<number> opens the same position against the computer.

How the 960 positions are built

Only the back rank changes; the pawns stay where they are. Three rules constrain which arrangements are legal, and together they leave exactly 960:

• The bishops go on opposite colours, one light and one dark, as they do in standard chess.
• The king stands between the two rooks. This is the rule that makes castling well-defined no matter how the pieces are shuffled.
• Black mirrors White exactly, so both sides face the same problem.

Positions are numbered 0 to 959 using the standard scheme, so a number here means the same position anywhere else. Position 518 is ordinary chess, the familiar RNBQKBNR. It is the quickest way to check that a generator is honest.

Castling in the position above

However the pieces start, castling always finishes in the same place as standard chess: after castling short the king is on g1 and the rook on f1; after castling long the king is on c1 and the rook on d1. The squares they come from are what change, which is why the panel above spells them out.

Full Chess960 castling rules →

Now train on it

Generating a position is the easy half. The hard half is seeing tactics on a board whose shapes you have never met. Try the free Chess960 puzzle trainer, or the 1,000-puzzle books.