Rules · 6 min read
The offside rule explained: position, phases and the calls that decide games
Offside is the most argued-about law in football and one of the simplest once you separate position from offence.
It is a position first, an offence second
A player is in an offside position if they are nearer to the opponents' goal line than both the ball and the second-last opponent. That is all the position means: it is not yet an offence, and a player can stand there for the whole match without breaking a rule.
The second-last opponent is almost always the last defender, because the goalkeeper counts as the last one. If two defenders are level with the attacker, the attacker is onside. Referees are taught to judge the moment of the pass, not the moment of the shot or the header.
When the flag stays down
There is no offside from a goal kick, a throw-in or a corner. A player who receives the ball in their own half is never offside, even if every opponent is in the other half. A player level with the second-last opponent is onside, and a pass played backwards cannot create an offside offence.
This is why defenders step up as a unit: the line is a tool to compress space, not a guarantee. One defender a yard deeper than the rest keeps the striker onside and the whole plan collapses.
Active play: the three ways to be punished
Being in an offside position becomes an offence only through involvement: interfering with play by touching the ball, interfering with an opponent by blocking their line of sight or challenging them, or gaining an advantage by playing a rebound off the post, the crossbar or an opponent.
Under the semi-automated offside system used in the Premier League, La Liga and UEFA competitions, a limb-tracking camera network and a chip in the ball generate the kick point and the line in seconds. The referee still makes the decision; the technology only draws the picture.
Quick answers
Is offside judged when the ball is played or when it is received?
When it is played. The position is frozen at the moment of the pass, even if the attacker runs back onside afterwards.
Can you be offside from a throw-in?
No. Throw-ins, goal kicks and corners are exempt, so a striker can stand behind the last defender at a throw and stay onside.
Why do some offsides take three minutes to check?
The system draws the line quickly, but officials still have to decide whether the attacker interfered with an opponent, which is a judgement call rather than a measurement.