If you have watched even ten minutes of soccer, you have seen it: a goal is scored, the crowd erupts, and then a flag goes up on the sideline. The referee waves off the goal. The stadium groans. The commentators start arguing.
That was offside.
It is the rule that causes more confusion — and more controversy — than anything else in the sport. Here is what it actually means.
The Basic Rule
A player is offside if all three of these things are true at the same moment:
- They are in the opponent’s half of the field
- They receive or are about to receive the ball
- When the ball is played to them, fewer than two opponents are between them and the goal (usually the goalkeeper + one defender)
If those three conditions are all met, the referee calls offside. The goal — if one was scored — is disallowed.
That is the whole rule. Everything else is just clarification.
The Simpler Way to Think About It
Ignore the legal language for a second. The spirit of the offside rule is this:
You cannot stand behind the last defender and wait for the ball to be passed to you.
Soccer without offside would be chaos. Every team would just park a striker directly in front of the opposing goalkeeper. The game would turn into a long-ball lottery. The offside rule forces players to time their runs, creates the tactical back-and-forth between attackers and defensive lines, and rewards skill over exploitation.
The Moment That Matters: When the Ball Is Played
The most important thing to understand is when the offside decision is made.
It is not when the player receives the ball. It is the exact moment the ball leaves their teammate’s foot.
This is why you sometimes see a player run past the last defender after a ball is played and still be ruled onside — because they were level with or behind the defender when the pass was made.
This is also why you see VAR (Video Assistant Referee) freeze-frame footage showing a player’s shoulder, armpit, or toe being an inch past the defensive line. The technology captures the single frame when the ball was kicked, and that frozen moment determines the call.
What Does Not Count as Offside
A few things that trip up new fans:
- You cannot be offside from a goalkeeper’s kick, corner kick, throw-in, or goal kick. These restarts reset the offside trap.
- Being offside is not an automatic foul. You are only penalized if you are involved in active play — receiving the ball, interfering with a defender, or distracting the goalkeeper.
- You have to be in the opponent’s half. A striker standing in their own half cannot be offside, no matter where the other defenders are.
VAR and the Armpit Lines
Since VAR was introduced at the 2018 World Cup, offside decisions have become both more accurate and more controversial.
The technology uses multiple camera angles and tracking data to freeze the frame at the exact moment a pass is made, then draws a line across the field to compare the positions of the attacker and the last defender.
In theory, this eliminates human error. In practice, it has led to goals being disallowed by a matter of centimeters — a shoulder, a heel, a single toe — and has generated fierce debate about whether the rule needs reforming.
For now, it stands. And when you see that freeze-frame image pop up on screen with the blue and red lines drawn across players’ bodies, you are watching the most technically demanding refereeing call in sports.
A Quick Example
France is attacking. A French midfielder plays a through ball toward the penalty area. At the exact moment the ball is played, the French striker is one step ahead of the last Spanish defender, with only the goalkeeper behind him.
Offside. Goal disallowed.
If the striker had been level with the defender — even half a step behind — it is onside. The pass was made at the right moment.
Timing is everything.
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