Offside (association football)

Offside is one of the laws in association football, codified in Law 11 of the Laws of the Game. The law states that a player is in an offside position if any of their body parts, except the hands and arms, are in the opponents' half of the pitch and closer to the opponents' goal line than both the ball and the second-last opponent.
Being in an offside position is not an offence in itself, but a player so positioned when the ball is played by a teammate can be judged guilty of an offside offence if they receive the ball or will otherwise become "involved in active play", will "interfere with an opponent", or will "gain an advantage" by being in that position. Offside is often considered one of the most difficult-to-understand aspects of the sport.

Significance

Offside is judged at the moment the ball is last touched by the most recent teammate to touch the ball. Being in an offside position is not an offence in itself. A player who was in an offside position at the moment the ball was last touched or played by a teammate must then become involved in active play, in the opinion of the referee, in order for an offence to occur. When the offside offence occurs, the referee stops play, and awards an indirect free kick to the defending team from the place where the offending player became involved in active play.
The offside offence is neither a foul nor misconduct as it does not belong to Law 12. Like fouls, however, any play that occurs after an offence has taken place, but before the referee is able to stop the play, is nullified. The only time an offence related to offside is cautionable is if a defender deliberately leaves the field in order to deceive their opponents regarding a player's offside position, or if a forward, having left the field, returns and gains an advantage. In neither of these cases is the player penalised for being offside; instead they are cautioned for acts of unsporting behaviour.
An attacker who is able to receive the ball behind the opposition defenders is often in a good position to score. The offside rule limits attackers' ability to do this, requiring that they be onside when the ball is played forward. Though restricted, well-timed passes and fast running allow an attacker to move into such a situation after the ball is kicked forward without committing the offence. Officiating decisions regarding offside, which can often be a matter of only centimetres or inches, can be critical in games, as they may determine whether a promising attack can continue, or even if a goal is allowed to stand.
One of the main duties of the assistant referees is to assist the referee in adjudicating offside—their position on the sidelines giving a more useful view sideways across the pitch. Assistant referees communicate that an offside offence has occurred by raising a signal flag. However, as with all officiating decisions in the game, adjudicating offside is ultimately up to the referee, who can overrule the advice of their assistants if they see fit.

Application

The application of the offside rule may be considered in three steps: offside position, offside offence, and offside sanction.

Offside position

A player is in an "offside position" if they are in the opposing team's half of the field and also "nearer to the opponents' goal line than both the ball and the second-last opponent." The 2005 edition of the Laws of the Game included a new IFAB decision that stated, "In the definition of offside position, 'nearer to his opponents' goal line' means that any part of their head, body or feet is nearer to their opponents' goal line than both the ball and the second last opponent. The arms are not included in this definition". By 2017, the wording had changed to say that, in judging offside position, "The hands and arms of all players, including the goalkeepers, are not considered." In other words, a player is in an offside position if two conditions are met:

Any part of the player's head, body or feet is in the opponents' half of the field.
Any part of the player's head, body or feet is closer to the opponents' goal line than both the ball and the second-last opponent.

The goalkeeper counts as an opponent in the second condition, but it is not necessary that the last opponent be the goalkeeper.

Offside offence

A player in an offside position at the moment the ball is touched or played by a teammate is only penalised for committing an offside offence if, in the opinion of the referee, they become involved in active play by:
; Interfering with play
; Interfering with an opponent
; Gaining an advantage by playing the ball or interfering with an opponent when it has
In addition to the above criteria, in the 2017–18 edition of the Laws of the Game, the IFAB made a further clarification that, "In situations where a player moving from, or standing in, an offside position is in the way of an opponent and interferes with the movement of the opponent towards the ball this is an offside offence if it impacts on the ability of the opponent to play or challenge for the ball."
There is no offside offence if a player receives the ball directly from a goal kick, a corner kick, or a throw-in. It is also not an offence if the ball was last deliberately played by an opponent. In this context, according to the IFAB, "A 'save' is when a player stops, or attempts to stop, a ball which is going into or very close to the goal with any part of the body except the hands/arms."
An offside offence may occur if a player receives the ball directly from either a direct free kick, indirect free kick or dropped-ball.
Since offside is judged at the time the ball is touched or played by a teammate, not when the player receives the ball, it is possible for a player to receive the ball significantly past the second-to-last opponent, or even the last opponent, without committing an offence, since an onside player is free to run to any position after the ball is played.
A player who was offside when their teammate played the ball but becomes onside when the ball is played by another player then ceases to be liable for an offside offence. That is, the determination of offside is reset each time the ball is played by a different onside player.
Determining whether a player is "involved in active play" can be complex. The quote, "If he's not interfering with play, what's he doing on the pitch?" has been attributed to Bill Nicholson and Danny Blanchflower. In an effort to avoid such criticisms, which were based on the fact that phrases such as "interfering with play", "interfering with an opponent", and "gaining an advantage" were not clearly defined, FIFA issued new guidelines for interpreting the offside law in 2003; and these were incorporated into Law 11 in July 2005. The new wording sought to define the three cases more precisely, but a number of football associations and confederations continued to request more information about what movements a player in an offside position could make without interfering with an opponent. In response to these requests, IFAB circular 3 was issued in 2015 to provide additional guidance on the criteria for interfering with an opponent. This additional guidance is now included in the main body of the law, and forms the last three conditions under the heading "Interfering with an opponent" as shown above. The circular also contained additional guidance on the meaning of a save, in the context of a ball that has "been deliberately saved by any opponent."

Offside sanction

The sanction for an offside offence is an indirect free kick for the opponent at the place where the offence occurred, even if it is in the player's own half of the field of play.

Officiating

In enforcing this rule, the referee depends greatly on an assistant referee, who generally keeps in line with the second-to-last opponent, the ball, or the halfway line, whichever is closer to the goal line of their relevant end. An assistant referee signals for an offside offence by first raising their flag to a vertical position and then, if the referee stops play, by partly lowering their flag to an angle that signifies the location of the offence:

Flag pointed at a 45-degree angle downwards: offence has occurred in the third of the pitch nearest to the assistant referee;
Flag parallel to the ground: offence has occurred in the middle third of the pitch;
Flag pointed at a 45-degree angle upwards: offence has occurred in the third of the pitch furthest from the assistant referee.

The assistant referees' task with regard to offside can be difficult, as they need to keep up with attacks and counter-attacks, consider which players are in an offside position when the ball is played, and then determine whether and when the offside-positioned players become involved in active play. The risk of false judgement is further increased by the foreshortening effect, which occurs when the distance between the attacking player and the assistant referee is significantly different from the distance to the defending player, and the assistant referee is not directly in line with the defender. The difficulty of offside officiating is often underestimated by spectators. Trying to judge if a player is level with an opponent at the moment the ball is kicked is not easy: if an attacker and a defender are running in opposite directions, they can be two metres apart in less than a second.
Some researchers believe that offside officiating errors are "optically inevitable". It has been argued that human beings and technological media are incapable of accurately detecting an offside position quickly enough to make a timely decision. Sometimes it simply is not possible to keep all the relevant players in the visual field at once. There have been some proposals for automated enforcement of the offside rule.