En passant

A pawn may capture an adjacent enemy pawn that has just advanced two squares as though it had moved only one square.

Also called: In passing, En passant capture

The adjacent pawn advances diagonally into the crossed square, and the pawn that moved two squares is removed. Source: Wikimedia Commons: En passant animation at 0:00.

How it works

  1. Have a pawn beside an enemy pawn immediately after that enemy pawn moves two squares from its starting square.
  2. On your very next move, move your pawn diagonally into the square the enemy pawn crossed.
  3. Remove the enemy pawn from the square where it finished.
Use it when
The capture is legal and wins material or improves your position; the right disappears if you make another move.
Watch for
En passant is optional, and it is illegal if the capture would leave your king in check.
Practice
Set up the position from both sides and verify the capture square before moving.