What is En Passant?

En passant (French for 'in passing') is a special chess rule that gives pawns the option to capture a pawn which has just passed it.

You may be surprised to learn that this is not a bug or a hack, but a legal chess move that has been part of the game for over 400 years, and has been an official chess rule since 1880.

Here's an example:

Black has just moved his pawn forward two spaces, and landed alongside the white pawn. What many beginners don't realize is that white has the option to capture the black pawn as if it had only moved one square instead of two.

White doesn't have to capture in this scenario, but if he doesn't, the option won't be there next turn. Imagine it as if the black pawn is moving past white's pawn. In the moment while it is moving past, white has the chance to attack it, but only in that moment. Once the pawn has successfully moved past (the turn is over), it can't be attacked by en passant anymore.

For a more in depth explanation of en passant, please read the following article: How to Capture En Passant!.