chess fen(Forsyth–Edwards Notation)

used to describe current position

 

in url 

 / is encoded as %2F

fen strings have six different fields separated by a space character.

1. Piece Placement 

It starts describing the content of each square, beginning from the eighth rank(row) and ending with the first. For each rank, squares begin from the first file and go to the eighth.

Empty squares are denoted by numbers from one to eight, depending on how many empty squares are between two pieces

 PNBRQK = white  piece  pawn,knight,bishop,rook,queen,king 

pnbrqk = black piece same

 

starting game 

 

 rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBN

 2. Active Color

who moves next w or  b

 

3. Castling Rights

Uppercase letters come first to indicate White's castling availability, followed by lowercase letters for Black's.

k q or - kingside,queenside or no castle

4. Possible En Passant Targets

If a pawn has moved two squares immediately FEN string adds the square behind the pawn in algebraic notation in its fourth field.

5. Halfmove Clock

how many moves both players have made since the last pawn advance or piece capture—known by chess programmers as the number of halfmoves

This field is useful to enforce the 50-move draw rule. When this counter reaches 100 (allowing each player to make 50 moves), the game ends in a draw.

 

6. Fullmove Number

The sixth and last field of the FEN code shows the number of completed turns in the game. This number is incremented by one every time Black moves. Chess programmers call this a fullmove.

chess.com fen

https://www.chess.com/analysis?fen=f1+f2+f3+f4+f5+f6

f1=qB6%2F8%2F5N2%2F3B4%2F8%2F2p5%2F1r1pNK2%2F7k

f1=qB6%2F8%2F8%2F3B4%2F4N3%2F2p5%2F1r1pNK2%2F7k

 

here %2F is url encoding of / as it conflicts with path / in browser

or manually https://www.chess.com/analysis

 

 

src

https://www.chess.com/terms/fen-chess 

https://en.wikipedia.org/wiki/Forsyth–Edwards_Notation

https://www.w3schools.com/tags/ref_urlencode.asp

https://thechessworld.com/articles/general-information/chess-notation-the-complete-guide/