In American football, “OT” commonly refers to overtime, which occurs when the score is tied at the end of regulation play. During overtime, each team gets an opportunity to possess the ball and attempt to score, with the game continuing until one team outscores the other. If the score remains tied after the overtime period, additional overtime periods may be played until a winner is determined.

In most professional and college football games, there is only one overtime period. However, in some specific situations, such as playoff games or certain collegiate conferences, rules may stipulate multiple overtime periods if the game remains tied after the initial overtime period.

For example, in college football, the NCAA adopted a rule in 2021 that after the second overtime period, teams are no longer allowed to kick extra points after touchdowns. Instead, they must attempt two-point conversions. If the game reaches a third overtime period, teams run alternating two-point conversion plays from the three-yard line, rather than starting possessions from the 25-yard line as in the first two overtime periods. This rule change was intended to expedite overtime play and reduce the number of plays in overtime, as well as to address player safety concerns.