In football, each team's goalkeeper defends his/her team's goal and has special privileges within the game. The goalkeeper's main job is to stop any penetration of the ball into the goal. The goalkeeper is the only player in the side who may use his or her hands and arms to catch, throw and save the ball, but only within his/her own penalty area. Goalkeepers are required to wear a distinctive color jersey, separate from the referee's jersey color and either team's regular jersey color, so the referee can easily identify them. There are no other specific requirements, but goalkeepers are usually allowed to wear additional protective gear such as padded clothing. Most goalkeepers also wear gloves to protect their hands and enhance their grip of the ball. Like every player on the pitch, they are required to wear shin guards.

The goalkeeper is allowed to catch the ball, and is also allowed to punch or deflect the ball away from the goal. The goalkeeper generally has a significant advantage on a ball high in the air, as he or she can raise their arms and play the ball before an attacker can attempt a header. When the keeper picks up the ball, they are allowed to kick it or throw it, or to place it on the ground and play it with his feet. The official Laws of the Game stipulate that once the goalkeeper has picked up the ball, he or she must redistribute it within six seconds; however, referees often use their discretion as long as the goalkeeper is not obviously attempting to waste time. Once the keeper establishes possession of the ball, opposing players are not allowed to attempt to play the ball and must give the goalkeeper room to attempt a kick.^{[citation needed]} If a ball is in the air and both the goalkeeper and a field player of the opposing team are challenging for the ball, advantage usually goes to the goalkeeper because he or she is not able to protect themselves.

Though the goalkeeper is generally allowed to use their hands in the penalty box area, they are not allowed to use their hands on balls that have been intentionally kicked to them by a teammate (it does not actually have to go backwards). In such situations, the goalkeeper may play the ball with their feet, but cannot pick the ball up. The rule applies only to a ball which is actually kicked. A ball which is headed or otherwise not kicked may be picked up by the goalkeeper without penalty. An infringement of this rule results in an indirect kick to the opposing team. The referee has some discretion in making this call. For example, a ball which is merely deflected by a teammate may still be picked up by the goalkeeper. The "back-pass" rule has been followed in international football and in most professional and amateur leagues since the early 1990s, but leagues for younger players may choose not to enforce the rule. The back pass rule is listed in Law 12 of the Laws of the Game.

As the goalkeeper is usually the team's only player who can see the entire field, they often act as the organizer of the team when it is defending, such as on a free kick or a corner kick. This means the goalkeeper needs to be loud, with a voice that can project over the defensive area of the pitch. In turn, the players on their team need to be able to listen and respond to directions called to them.