Animation of a referee raising the flag

That’s a clear offside! But why?

As Ted Lasso said to Trent Crimm when the British journalist asked the American coach if he could explain the offside rule in the second episode of the Apple TV show: “It ain’t easy to explain, but you know when you see it.” Well, we’ll try to explain the offside rule better than Supreme Court Justice Potter Stewart’s attempt to define obscenity, the phrase to which Lasso was referring.

In fact, Law 11 of international soccer’s official rule book is pretty simple:

A player is in a legal position (not offside) when there are at least two players from the other team between him and the opposing goal line at the moment the ball is passed to him.

The two players could be a goalkeeper and a field player or two field players.

If there is only one defender (or none) between the attacker and the opposite goal at the moment of the pass, then the player is in an offside position.

One key thing to remember: The offside rule is based on where the attacking player is at the moment the ball is passed, not where he is when he receives the ball.

But there are exceptions, footnotes, and, sometimes, you don’t know when you see it.

And why is that not offside?

Now it starts to get a bit more complicated, because for a player to be offside, he has to meet some conditions. For instance, he has to be in his opponent’s half of the field, be in front of the ball when it is passed to him, and attempt to play the ball.

Let’s see how these look on a soccer pitch.

In a soccer game there are usually 22 players on the field, 11 for each team. But to explain this, we’ll display two players from each team, plus the assistant referee.

First thing: A player cannot be offside if he is in his own half of the field. So you might see a counterattack that seems offside, but it’s not.

A player can only be offside in the other team’s half.

If the player who receives the ball is behind the ball at the moment of the pass he cannot be offside.

Only players who are in front of the ball when it is passed can be in an offside position.

And a player has to intend to go for the ball to earn an offside call; he can’t just be a bystander. To explain this, we’ll add another yellow team player.

If a player who is offside at the moment of the pass — the yellow team player in the lower right corner — gets out of the way rather than going toward the ball or interfering with an opponent, he is fine. Another player who wasn’t offside when the pass was made can play the ball legally.

If an offside offense occurs, the referee awards a free kick to the other team at the spot where the offside player was at the time the ball was played.

And there are some scenarios in which players cannot be called offside: a goal kick, a throw-in, a corner kick or if the player receives the ball from an opponent who deliberately plays the ball.

A matter of inches

In most cases when an offside is called, a player’s entire body is offside. But if it is close, it can come down to body parts. What if an attacker’s arm is closer to the goal line than a defender’s foot? Is that an offside? Let’s see.

The parts of the body that can be offside are the same that can touch the ball, so everything but the arms counts.

Head

Arms

Trunk

Legs

The parts of the body that can be offside are the same that can touch the ball, so everything but the arms counts.

Head

Arms

Trunk

Legs

The parts of the body that can be offside are the same that can touch the ball, so everything but the arms counts.

Head

Arms

Trunk

Legs

So back to our question: No, if the attacker’s hand or arm is closer to the goal than the defender’s foot, there is no offside. But sometimes it can be very hard to tell, even in slow-motion replay.

In this case the line that marks the offside is the foot of the defender. At the moment of the pass, the hand of the attacker is his only body part ahead of the defender's foot. So it’s not an offside.

In this case the line that marks the offside is the foot of the defender. At the moment of the pass, the hand of the attacker is his only body part ahead of the defender's foot. So it’s not an offside.

In this case the line that marks the offside is the foot of the defender. At the moment of the pass, the hand of the attacker is his only body part ahead of the defender's foot. So it’s not an offside.

But take a close look at this next play:

Do you see how the attacker's left foot is ahead of the defender’s feet? It’s not as easy to catch this offside. That’s why the referee has some help, from humans and machines.

But take a close look at this next play:

Do you see how the attacker's left foot is ahead of the defender’s feet? It’s not as easy to catch this offside. That’s why the referee has some help, from humans and machines.

But take a close look at this next play:

Do you see how the attacker's left foot is ahead of the defender’s feet? It’s not as easy to catch this offside. That’s why the referee has some help, from humans and machines.

The referees

The head referee is the one moving all around the field. Normally, it’s impossible for him to tell if a player was in an offside position. So he needs help from two assistant referees that move along the sides of the field, one on each half. Assistants refs try to stay even with the second to last defender so they are in a good position to see if anyone is offside.

Assistant referee

Head

referee

Assistant referee

Assistant referee

Head

referee

Assistant referee

Assistant referee

Head

referee

Assistant referee

Assistant referees communicate with the head referee by moving their flags in different ways for a foul, a corner kick, a goal kick and, of course, an offside.

The assistant referee indicates an offside by moving the flag in two steps.

1.

Raising the flag…

2.

And then lowering it depending on where

the offside player is:

On the near side

of the field

In the middle

of the field

On the farside

of the field

The assistant referee indicates an offside by moving the flag in two steps.

1.

Raising the flag…

2.

And then lowering it depending on where

the offside player is:

On the near side

of the field

In the middle

of the field

On the far side

of the field

The assistant referee indicates an offside by moving the flag in two steps.

1.

Raising the flag…

2.

And then lowering it depending on where

the offside player is:

On the near side

of the field

In the middle

of the field

On the far side

of the field

But as we saw in the first game of this World Cup, sometimes the human eye can’t tell if a player is in an allowable or unallowable position. To help correct mistakes, FIFA, the sport’s international governing body, introduced video assistant referees (VAR) in the 2018 World Cup, after trial runs in some less prominent competitions. A VAR monitors video during each game from a control room in the stadium and alerts the on-field referee through his earpiece that a mistake may have been made. The referee may then either change a call, let the call stand or stop the game and look at the video replay. Offside, however, is reviewed only if there’s a goal.

[What to know about video review at the World Cup]

In addition, FIFA announced this summer that this will be the first World Cup to use semi-automated offside technology as part of its video review system. The new technology uses 12 cameras mounted beneath the stadium’s roof to track the ball and each player 50 times per second to help the referees. The ball also features a sensor that sends data to the video operation room 500 times per second, and alerts the VAR if a player gets the ball in an offside position. The VAR will then manually check this call — with the help of an automatically generated offside line — before making a recommendation to the referee.

So don’t worry if you don’t catch every offside. Even in a big event like the World Cup — with referees, dozens of cameras and multiple reviews — there still will be some doubts. Maybe obscenity actually is easier to know when you see it.