Level with the last defender is onside

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• Note

  Hands and arms never count for offside

  For every player including goalkeepers, only parts that could legally score are considered — head, body and feet — and the upper boundary of the arm is the bottom of the armpit. A shoulder in front can decide a call; an outstretched arm cannot.

• Note

  Level is onside

  The test is NEARER to the goal line than the ball and than the second-last opponent. A player exactly level with either is onside, which is why the tightest calls come down to which side of a line a toe was on.

• Read this

  The picture freezes when the ball is played, not when it is received

  Position is judged at the moment a team-mate plays or touches the ball. Where the attacker was when the ball ARRIVED is irrelevant, and running onto a ball from an onside position is exactly what the law permits.

• Read this

  An offside position is not an offence

  A player can stand in an offside position all afternoon without committing anything. The offence requires involvement in active play — interfering with play, interfering with an opponent, or gaining an advantage — at the moment the ball is played.

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  Applying the law is the easy half

  This computed a verdict from positions and judgements you supplied. In a real match the argument is almost never about the procedure — it is about where a shoulder was in the frame the ball was struck, and whether a touch was deliberate. Change those inputs and the answer changes with them.