Offside Explainer / Diagram Tool
Move the ball, the second-last defender and the attacker to see whether the attacker is offside, with the offside line drawn on a pitch and the reason explained.
About this tool
Offside is judged at the moment a team-mate plays or touches the ball. An attacker is in an offside position if they're in the opponents' half and nearer the goal line than both the ball and the second-last opponent. The goalkeeper usually counts as the last opponent, so the second-last is normally the deepest outfield defender. Level with the second-last defender, or level with the ball, is onside. Hands and arms don't count; any part of the head, body or feet that can score does.
Being in an offside position isn't an offence on its own: the referee only gives offside if the player then gets involved, by playing the ball, blocking a defender's line of sight or challenging for it. There's no offside from a goal kick, a throw-in or a corner. The yellow dashed line in the diagram is the offside line; anywhere in the shaded area past it is an offside position.