What en passant means
En passant lets a pawn capture another pawn that just moved two squares from its starting square and landed beside it. Your pawn captures as if that pawn had moved only one square.
The captured pawn is removed from the square it landed on, while your pawn moves diagonally behind it.
When en passant is legal
- Your pawn must be on its fifth rank.
- The opponent's pawn must move two squares from its starting square.
- The opponent's pawn must land directly beside your pawn.
- You must capture en passant immediately on your next move.
The key timing rule
If you do not play en passant right away, the right disappears. You cannot wait one move and come back to it later.
Quick test
Ask: did the enemy pawn just jump two squares and land next to my pawn? If yes, en passant may be available now.