In most levels of professional American football, the two-minute warning is given when two minutes of game time remain on the game clock in each half of a game or overtime, i.e. near the end of the second and fourth quarters. The suspension of play is two minutes long, the same as the short two-minute intermissions between quarters within each half. There is an additional two-minute warning in the rare event only two minutes remain in an overtime period. However, in the postseason, where games continue indefinitely if there is no score, there is no two-minute warning in the first overtime, but if the second overtime, or any subsequent even overtime, is still tied with two minutes remaining (which has never happened), there will be a two-minute warning. If the football is in play when the clock reaches 2:00, the two-minute warning is called immediately after the play concludes, when the ball is declared dead. The two-minute warning stops the game clock in all cases.
The origins are from the early years in the National Football League (NFL) when the official game time was kept by a member of the officiating crew, with the stadium clock being unofficial. Its purpose was a checkpoint to ensure that the teams knew how much time remained in the game. In the early 1960s the upstart American Football League (AFL) made the stadium clock the official game time, a change followed later in the decade by the NFL, shortly before its merger with the AFL. By then, television was an important factor in professional football, so the two-minute warning was retained as a commercial break and to serve as "tension building" time, and thus has become an important part of the game's flow.
In addition to those practical purposes, gradually, some rules have evolved that are unique to the final two minutes of each half and overtime. There is no special event at the ends of the first and third quarters, aside from swapping end zones, so there is no two-minute warning then, only at the halves, except as implemented in Pro Bowls from 2014 to 2016, and since 2019.
The following situations result in a 10-second game clock runoff if the team in possession of the ball is trailing or the game is tied and the team in possession of the ball has no timeouts remaining in that half/overtime. If 10 or less seconds remain in the half/overtime/game, the period/game will end by such runoff.
If a player is injured and his team has timeouts remaining in that half/overtime, the timeout is automatically charged to that team to allow the injured player to be removed from the field. If a team is out of timeouts, they are allowed an otherwise-excessive "fourth timeout" (or third if overtime). However, to minimize the feigning of injuries to save game clock time, any subsequent injuries after the fourth timeout result in a five-yard penalty. Besides the excessive timeout, there is a 10-second runoff (if it was an offensive player that was injured) or the play clock is reset to 40 seconds (if it was a defensive player).
Exceptions to the above include if the other team called a timeout immediately after the previous play to save time on the clock; the injury was caused by a foul by an opponent; or the previous play resulted in a change of possession, a successful field goal, or was a conversion attempt.
The period of time between the two-minute warning and the end of the half is known as the two-minute drill. During this time, clock management becomes a more important aspect of the game, since by proper manipulation of the game clock, a team can, if trailing, prolong the game long enough to secure a score, or if in the lead, hasten the half's end before the opponent can score.
If the leading team has the ball on first down with less than two minutes to go in the game and the opposing team has no timeouts remaining, the quarterback can often safely end the game by taking a knee thrice consecutively without risking injuries or turnovers. This is because at the end of each play, the offensive team can take up to 40 seconds to start running the next play.
The CFL has a three-minute warning.Indoor American football leagues historically used a one-minute warning once a minute remained in the half/overtime. No comparable rule exists at the high school or college levels; at the high school level, the officials are instructed to inform each sideline when three minutes remain in a half, but the rule does not stop the game clock.