What is offside, actually?

The single most common misunderstanding: offside is judged at the instant a teammate plays the ball, not when it arrives. A player can be level or behind the defensive line when the pass is struck and then sprint yards ahead before receiving it — still onside, because the position that matters was already locked in the moment the ball left their teammate's foot.

The actual rule (IFAB Law 11): an attacking player is in an offside position if, at the moment the ball is played to them, they're nearer to the opponents' goal line than both the ball and the second-last opponent — and they're in the opponents' half of the pitch. The "second-last opponent" is usually, but not always, the last outfield defender, since the goalkeeper normally counts as one of the two.

This is the part that trips people up most: being in an offside position isn't illegal by itself. It only becomes a punishable offense if that player then becomes involved in active play — by touching the ball, interfering with an opponent's ability to play it, or clearly gaining an advantage from the position (for example, playing a rebound off the post or goalkeeper while offside).

A player can stand in an offside position all game, completely uninvolved in the play, and nothing gets called — the whistle only comes once they actually engage with the ball or an opponent from that position.

There's no offside offense if a player receives the ball directly from a goal kick, a throw-in, or a corner kick — regardless of their position. And a player level with the second-last defender (not nearer) is onside, not offside — "level" favors the attacker, which is exactly why so many close calls come down to a millimeter on the VAR line.

A still image can only show one frozen instant — offside really clicks when you watch the defensive line and the pass happen together. Sportoum's Football module includes an interactive offside diagram built for exactly that.