Forsyth-Edwards Notation
File type: Various data file
Files with the fen file extension contain a chess position written in Forsyth-Edwards Notation (FEN).
FEN files are mainly used by chess programs and can be exchanged when analyzing positions or solving chess problems.
File type category:
Various data file
Date updated: November 6, 2026
Forsyth-Edwards Notation is a plain-text format that describes a chess position using ASCII characters. A FEN record normally stores the piece placement, the active color, castling availability, en passant target square, halfmove clock, and fullmove number.
The fen file extension is commonly used for files containing these records. Chess programs can use a FEN file to load a position for analysis, play, or problem solving, and the format also serves as a compact exchange format between chess applications.
FEN is not tied to one vendor or operating system. It remains in use because it provides a concise way to share a chess position, although it describes a position rather than the complete move history of a game.
Open a fen file in a chess program that supports FEN import or position setup. The program should display the described position on a chessboard.
A plain-text editor can also open the file and show its contents, but it will not interpret the notation as a chess position.
A fen file is already a text representation of one chess position, so it usually does not need conversion. Chess programs that support FEN can often import the position and export it in another supported position or game format.
Converting a FEN position to a complete game record is not possible without additional move data, because FEN does not contain the game's move history.
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