American football rules

Substitutions can be made between downs, which allows for a great deal of specialization as coaches choose the players best suited for each particular situation.

The referee controls the clock and stops it after any incomplete pass or play that ends out of bounds, a change of possession of the ball from one team to the other, field goal tries, and kickoffs.

Some high schools employ a mercy rule in which the clock runs continuously after one team's lead over the other achieves a certain number of points.

The other team can win with a touchdown, tie with a field goal leading to sudden death, or lose if they fail to score.

The team that wins the coin flip has the option either to receive the kickoff or choose the side of the field they wish to defend.

The NFL's overtime rules are often subject to criticism, as a team that loses the coin toss and goes on to concede the touchdown does not get a chance for their offense to take the field.

The coin toss winner won approximately 60% of overtime games under that rule, rather than the 50% expected by random chance.

Denver won the game on the first play in overtime, an 80-yard touchdown pass from Tim Tebow to Demaryius Thomas.

The rule was formally adopted for the 2012 season,[10] and the first game in which both teams scored in overtime was a 43–37 victory by the Houston Texans over the Jacksonville Jaguars on November 18, 2012.

In the NFC title game, the New Orleans Saints won the coin toss but an interception allowed the Los Angeles Rams to drive into range to kick the game-winning field goal.

In the AFC Championship held later that day, the New England Patriots won the coin toss and on their first drive scored the game-winning touchdown over the Kansas City Chiefs.

The overtime consisted of one 15-minute period, which was played in its entirety and divided into two halves of 7½ minutes each, with each half starting with a kickoff by one of the teams.

Their possession ends when they score either a touchdown or a field goal, turn the ball over via a fumble or an interception, or fail to gain a first down.

If the score remains tied after both teams have completed a series, the procedure is repeated in a second overtime period.

[17] In the second incarnation of the United States Football League, teams played three (at least two) rounds of two-point conversions from the three-yard line.

In college games, the team that wins the toss defers their choice to the start of the second half over 90% of the time.

The original incarnation of the XFL did not implement a coin toss; instead, an event took place called the "opening scramble", in which one player from each team fought to recover a football 20 yards away to determine possession.

A defensive lineman's job is typically to put pressure on the opposing team's quarterback by rushing the offensive line.

For the 2024 NFL season, kickoffs were overhauled to limit injuries and promote returns, utilizing a similar system to the UFL.

The uncommon safety is scored if a player causes the ball to become dead in his own end zone; two points are awarded to the opposing (usually defending) team.

In the NFL, if the receiving team elects to attempt this and time expired during the punt, the half/overtime is extended with an untimed down.

Every crew will consist of a referee, who is generally in charge of the game and watches the action on the quarterback and in the offensive backfield; an umpire, who handles spotting the ball and watches the action on the offensive line; and a head linesman, who supervises the placement of the down box and line-to-gain chains.

Because football is a high-contact sport requiring a balance between offense and defense, many rules exist that regulate equality, safety, contact, and actions of players on each team.

Thus, an elaborate system of fouls and penalties has been developed to "let the punishment fit the crime" and maintain a balance between following the rules and keeping a good flow of the game.

But if a defensive foul results in the ball advancing beyond the offense's first-down objective, the next play will be the first down of a new series.

Under college rules, any accepted penalty when the time has expired at the end of any quarter results in an extension for one untimed down.

In the NFL, with three exceptions, no penalty may move the ball more than half the distance toward the penalized team's goal line.

These exceptions are defensive pass interference (see the discussion of that foul for more details), intentional grounding, and offensive holding – but in this last case, the exception pertains only if the infraction occurs within the offensive team's own end zone, in which case an automatic safety is assessed (intentional grounding from the end zone also carries an automatic safety).

Beginning in the 2011 NFL Season, an instant replay review by the booth official will now be automatic for every play ruled by the referees on the field to have scored points.

Some of the major rule differences between NFL and college football include: In the regular season, only one 10-minute overtime is played and games may end in a tie.