What is FEN, and why should I care?

FEN stands for "Forsyth-Edwards Notation." It is a standard method for describing chess positions using simple text. With a little bit of practice, you will be able to describe positions using FEN.

This skill can pay off in several ways. When you drop the FEN code into your kibitzing at Chessgames.com, diagrams will automatically appear. Also, there are many commercial chess programs which use FEN.

The first thing you have to understand is that the board is broken into eight ranks. (A rank is a chess term for a row of eight squares running from left to right.) Each rank is converted into a string, then all eight of these strings are compacted together separated only by slashes (/).

Let's look at an example:

Now let's learn how to come up with one of these strings like "pp3nPp" that represent a rank. Look at the 7th rank of the diagram in the example above. From left to right, you see: two black pawns, three empty spaces, a black knight, a white pawn, and a black pawn. In FEN, two black pawns are pp. Three empty spaces is simply 3, a black knight is n (not "k" -- that's used for the king!), a white pawn is P (remember, all white pieces are in capital letters), and a black pawn is p. Putting all this together, you get pp3nPp which represents that one rank.

If you want to show a diagram in a message at Chessgames.com, simply insert the FEN code into your text. It will automatically appear as a small diagram, with a link to a larger diagram. For example, if you type this:

White to play and draw. (Richard Reti, 1921) 7K/8/k1P5/7p/8/8/8/8

Others will see this:

White to play and draw. (Richard Reti, 1921) click for larger view

That's all there is to it!

IMPORTANT NOTE: When posting to Chessgames, this feature should be used with discretion. Diagrams generated from FEN strings consume a lot of computer resources, and also make pages load slower. Therefore, we request that you do not post too many diagrams in any single message, and never use this feature for decorative purposes. Thank you!

Sure! Most modern chess programs provide support for FEN and allow you to copy or paste FEN positions.

There are also some websites that perform this function. The clever programmers at Lokasoft have developed an interface to the Nalimov Endgame Tablebase which allows you to set up positions for endgame analysis. A handy side-effect of their program is that it shows you the FEN for any position you set-up.

Not really--FEN is actually more complicated than what we've described here. True FEN includes information regarding whose move it is, castling rights, en passant, the 50 move rule, etc. None of this matters if you are just using FEN to post diagrams to Chessgames, but if you are curious to learn more, please see Wikipedia's article on Forsyth-Edwards Notation.