What is offside in football?

The rule combines two tests. The first is position: at the exact moment a teammate touches the ball, the player must be in the opponent's half and nearer to the goal line than both the ball and the second-last opponent. Because the goalkeeper is usually the deepest player, the practical reference point is most often the last outfield defender. The second test is involvement: standing in an offside position is not an offence by itself. The player must play the ball, interfere with an opponent, or gain an advantage from that position.

Everything is judged at the moment the ball is played, not when it arrives. A player who starts behind the ball and outruns the defence is onside; a player who starts ahead of the second-last defender is offside even if they drop back to collect the pass. Head, body and feet all count in the judgement, while arms and hands do not, since a goal cannot be scored with them.

The law carries clear exceptions. There is no offside when the ball comes directly from a goal kick, a throw-in or a corner kick. A player in their own half, level with the second-last opponent, or behind the ball is never offside. Being level is enough: the attacker does not need to be clearly behind the defender.

A deliberate play by a defender also resets the situation in most cases: if an opponent controls and plays the ball intentionally, an attacker who was in an offside position may take it without penalty. A save is different. Deflections off the goalkeeper or a defender making a last-ditch block do not reset offside, so an attacker who was offside when the shot was struck is still penalised.

An offside goal is a goal ruled out because an attacker involved in the move was offside when the ball was played. In matches with VAR, assistant referees are told to delay the flag in tight situations and let the attack finish. If the ball ends up in the net, the video assistant referee reviews the position frame by frame, identifies the moment of the pass and draws lines on the attacker and defender. Goals are checked automatically, so a marginal offside cannot slip through unexamined.

Semi-automated offside technology speeds this up. Dedicated cameras track each player's limbs many times per second, and the system generates an automatic alert when an offside position coincides with the pass. Humans still validate the kick point and the question of interference, which is why the final decision always belongs to the officials.