Position is not the offence

Law 11 splits offside into two distinct things: being in an offside position and being penalised for offside. The first is just geometry — where the player is when the ball is played. The second is what they do next. Only the second is an offence.

What counts as "active involvement"

A player in an offside position is only penalised when they:

• Touch the ball played or touched by a teammate
• Challenge an opponent for the ball
• Gain an advantage from being in that position — for example, a rebound off the post, a deflection off the goalkeeper, or a deliberate save by a defender

If none of those happen, the offside player is treated as inactive. The flag stays down.

The flag delay

You'll often see assistants hold their flag rather than raise it instantly. That's deliberate. The instruction is to wait until involvement is clear — to avoid killing a goal that wouldn't actually have been offside. If the ball runs through to a different attacker who is onside, the original offside player is treated as never involved.

Common cases that confuse fans

• The blocking effect on the goalkeeper. If an offside player is in the keeper's line of sight or blocks their movement, that counts as interfering with an opponent — even without a touch.
• The rebound. If the ball comes back off the post or the keeper to an offside-positioned attacker, that's gaining an advantage. Offside.
• The deliberate save by a defender. A save by a defender (not a deflection) is treated like a goalkeeper save for offside purposes — a rebound from it puts an offside player in offence.

Why the rule exists in this form

The point of the active/inactive split is to keep the game flowing. A player standing in an offside position who has no impact on the play shouldn't kill the action. The law was rewritten in 2005 to make this explicit.