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Rules & notation

FEN

Forsyth–Edwards Notation

A single line of text that captures an exact position — pieces, side to move, castling rights and more.

A FEN string encodes the whole board rank by rank, then whose move it is, the castling rights, any en-passant square, and the move counters. It lets you share or set up any position instantly.

Engines, puzzle sets, and analysis boards all speak FEN — paste one in and the position appears.

Why it matters

FEN is how positions travel between people and programs; every serious chess tool reads and writes it.

The mistake everyone makes

Editing a FEN by hand and producing an illegal position (two kings in check, impossible castling rights).

Related terms

PGN
The standard text format for recording a whole game — its moves, players, result and comments.
Algebraic notation
The standard way to record moves: files a–h, ranks 1–8, so e4 and Nf3 mean exact squares.
Promotion
A pawn reaching the last rank becomes any piece you choose — almost always a queen.
En passant
A special pawn capture of a pawn that just advanced two squares, as if it had moved only one.

See FEN in your own games

Play the engine, train tactics, and analyse your games — ChessRanger points out these patterns as they come up so the word turns into a skill. Free to start.

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