In short: A way of writing a whole chess position on a single line of text.
Also called Forsyth–Edwards Notation.
A chess game can be saved move by move, but sometimes you only want to describe a single position, for example a puzzle or a position to analyze. That is what FEN is for. The whole position fits on one line:
rnbqkbnr/pp1ppppp/8/2p5/4P3/5N2/PPPP1PPP/RNBQKB1R b KQkq - 1 2
The six fields
A FEN has six parts, separated by spaces:
| Field | In the example | Meaning |
|---|---|---|
| The pieces | rnbqkbnr/…/RNBQKB1R | The ranks from the eighth to the first, separated by slashes. Each rank is read from a to h. |
| To move | b | w if White is to move, b if Black is. |
| Castling | KQkq | Which castling moves are still possible: K and Q for White kingside and queenside, k and q for Black. A dash if nobody can castle. |
| En passant | - | The square behind a pawn that has just moved two squares, otherwise a dash. |
| Halfmove clock | 1 | The number of half-moves since a pawn moved or a piece was captured. Used for the 50-move rule. |
| Move number | 2 | The number of the move in progress. It goes up after each Black move. |
How to read the pieces field
- Each piece has a letter: K king, Q queen, R rook, B bishop, N knight and P pawn.
- Capital letters are white pieces, small letters black.
- A number means that many empty squares in a row.
8is a completely empty rank.
The part 2p5 in the example is the fifth rank: two empty squares, a black pawn on c5 and then five empty squares.
A small trap. Under the original standard, the en passant square is written after every two-square pawn move. Some programs write it only when an en passant capture is actually possible. You will meet both.
Where does FEN come from?
FEN builds on a system that the Scottish journalist David Forsyth published in 1883. In the 1990s Steven J. Edwards extended it so that computers could use it, as part of the same standard as PGN. Hence the name: Forsyth–Edwards Notation.
Frequently asked questions
Does a FEN look different in other languages?
No. FEN is an international standard and always uses the English letters K, Q, R, B, N and P, so a FEN looks the same in every language.
What is the difference between FEN and PGN?
A FEN describes a single position. A PGN describes a whole game, move by move.
Updated October 31, 2026