What Is Offside in Football? The Rule, Examples, and Edge Cases

IFAB Law 11 has two halves. Position and involvement. A player is in an offside position if all three of these are true at the moment a teammate plays the ball:

• They are in the opposition half. A player cannot be offside in their own half.
• They are closer to the goal-line than the ball. Level with the ball is not offside.
• They are closer to the goal-line than the second-last defender (which is typically the deepest defender excluding the goalkeeper).

Even an attacker in an offside position can avoid being penalised in three situations:

• Goal kick. No player can be offside from a goal kick.
• Throw-in. No player can be offside from a throw-in.
• Corner kick. No player can be offside from a corner kick.

Three forms of involvement that turn an offside position into an offence:

• Receiving the ball. The most obvious — the attacker plays / touches the ball after a teammate played it.
• Interfering with an opponent. Blocking the goalkeeper's line of sight, challenging an opponent, or making a movement that affects an opponent's ability to play the ball.
• Gaining advantage. A typical example: an attacker in an offside position rebounds off the post or off a defender, then plays the ball — they have gained advantage.

Offside is judged at the moment the ball is played by a teammate — not the moment the receiver plays it. This is the most-misunderstood part of the rule.

Example: An attacker is in an onside position when their teammate kicks the ball, then runs into an offside-position area to receive it. This is NOT offside — they were onside at the moment-of-pass.

Five offside scenarios fans should recognise:

• Through-ball offside. A through-ball is played to a striker who has run beyond the back line; the ref / VAR judges body parts at the moment-of-pass.
• Last-defender offside. A defender plays the attacker onside by being deeper than the attacker. If the second-last defender steps up just before the moment-of-pass, the attacker is offside.
• Phase-of-play offside. An attacker initially in offside position becomes involved later in the same phase — still offside.
• Deflected ball offside. A defender deflects a pass to an offside-position attacker. The attacker is still offside (not "played onside" by the deflection).
• Chip-over-the-defender offside. A common goal-line scenario where the attacker times their run; SAOT routinely catches small offsides here.

How modern technology adjudicates offside:

• VAR. Manual line-drawing on a freeze-frame at the moment-of-pass. Took 60-90 seconds historically.
• SAOT (Semi-Automated Offside Technology). Multi-camera tracking + AI body-point detection automates the line at the moment-of-pass. Decisions take 25-30 seconds.
• Daylight test. Some leagues use a "daylight" margin — if there's no clear daylight between the attacker and the last defender, the on-field decision stands.
• IFAB review. IFAB has discussed introducing a "thickness" margin to avoid 1cm offsides; not yet implemented.

Three key historical changes:

• 1925. Number of defenders required between attacker and goal reduced from 3 to 2. This change is what created the modern WM formation and increased goal-scoring.
• 1990. "Level with" the second-last defender no longer counted as offside — the attacker just had to not be ahead of the line.
• 2005-2013. Definition of "active" / "interfering" tightened multiple times to make the rule simpler for referees.
• 2022. SAOT first used at a senior World Cup (Qatar 2022), automating moment-of-pass decisions.