En passant, French for 'in passing', is the least known rule in chess and surprises many new players. When a pawn advances two squares from its starting square and lands right beside an enemy pawn, the enemy pawn may capture it diagonally as if it had moved only one square.
Conditions for en passant
- The capturing pawn must be on its fifth rank: a white pawn on the 5th rank, a black pawn on the 4th.
- The enemy pawn must have just advanced two squares from its starting square, landing right next to the capturing pawn.
- The capture must be made on the very next move. If any other move is played, the right is lost for good.
Example
White has a pawn on e5. Black pushes the d7 pawn two squares to d5, landing next to the white pawn. On the very next move White may play exd6: the white pawn moves to d6 and the black pawn on d5 is removed. It is written exd6 or exd6 e.p.
Why does the rule exist?
The pawn's two-square first move was introduced centuries ago to speed up the game. But it allowed a pawn to slip past a square controlled by an enemy pawn. En passant closes that loophole and preserves the capture the enemy pawn would have had if the pawn had moved one square.
Where you meet it in practice
- In puzzles: en passant is sometimes the only winning or mating move, and is used precisely because it is easy to overlook.
- In endgames: racing passed pawns where gaining a tempo matters.
- In openings: structures with pawn chains such as the French Defense often offer en passant chances.
💡 En passant is optional. But if it is the only legal move, for example the only way out of check, it must be played.