FEN — short for Forsyth–Edwards Notation — is a compact, single-line text string that captures one chess position exactly: where every piece stands, whose turn it is, castling rights, en passant, and the move counters. Paste a FEN into any chess app and it rebuilds the position instantly. It’s the standard way to share a snapshot of a game.
Unlike PGN (which records a whole game, move by move), a FEN describes a single frozen moment. The starting position looks like this:
rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1The six fields, decoded
A FEN is six fields separated by spaces:
| # | Field | In the example | Means |
|---|---|---|---|
| 1 | Piece placement | rnbqkbnr/... | Ranks 81, each row separated by /. Uppercase = White, lowercase = Black, digits = that many empty squares. |
| 2 | Side to move | w | w = White to move, b = Black. |
| 3 | Castling rights | KQkq | K/Q = White can castle king/queen-side; k/q = Black. - if none. |
| 4 | En passant target | - | The square a pawn can be captured on en passant, or - if none. |
| 5 | Halfmove clock | 0 | Half-moves since the last capture or pawn move (for the 50-move rule). |
| 6 | Fullmove number | 1 | Starts at 1, increments after each Black move. |
Now watch it change. After 1.e4, the FEN becomes:
rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1Notice three things: the white pawn moved (4P3 on the 4th rank, and PPPP1PPP shows the gap), the side to move flipped to b, and the en passant field is now e3 — the square Black could capture on if it had a pawn in position.
Related terms
- PGN — records the whole game, where FEN records one position.
- Algebraic notation — the move language FEN’s cousins are built from.
- Background: files, ranks, and diagonals and chess notation explained.
- Back to the chess glossary.
Mini-FAQ
Which rank comes first in a FEN? Rank 8 (Black’s back rank) is written first, down to rank 1. Within each rank you read left to right, a-file to h-file.
What does the number after a piece letter mean — wait, there isn’t one?
Right — FEN never puts numbers next to a piece. Digits stand alone and mean “this many empty squares in a row.” So 3P4 = three empties, a pawn, four empties.
Written and fact-checked by the Chess Lab Academy Editorial Team (AI-assisted, human-edited) · Format cross-checked against Wikipedia; example FEN strings legality-verified with python-chess · Last verified 2026-07-13 · Sources · How we verify content.