In gridiron football, replay review is a method of reviewing a play using cameras at various angles to determine the accuracy of the initial call of the officials. An instant replay can take place in the event of a close or otherwise controversial call, either at the request of a team's head coach (with limitations) or the officials themselves.
Replay reviews are utilized in some high school games, and also for many games at the college level and above. Before the 2019 season, the National Federation of State High School Associations (NFHS), which establishes the rules for most high school and youth organizations in the United States (though not for Texas high schools), did not allow replay reviews even when the equipment exists to enable the practice. Effective in 2019, NFHS gave its member associations the option to allow replay review, but only in postseason games. In those leagues that utilize replay reviews, there are restrictions on what types of plays can be reviewed. In general, most penalty calls or lack thereof cannot be reviewed, nor can a play that is whistled dead by the officials before the play could come to its rightful end.
American and Canadian football leagues vary in their application and use of instant replay review.
By league
National Football League
The NFL first adopted a limited Instant Replay system in 1986. It remained in place through 1991. The current system was put into use in 1999, adding the opportunity to "challenge" on-field calls of plays. The current system mirrors a system used by the now defunct USFL in its final season, 1985. Each coach is allowed two opportunities per game to make a coach's challenge. Starting in 2004, the rule was amended to award a third challenge if both of the original two challenges were successful.
A challenge can be made on certain reviewable calls on plays that begin before the two-minute warning and only when a team has at least one timeout remaining in the half. Up until the 2005 season, coaches could signal a challenge via an electronic pager, now used only by the replay assistant. The coach now throws a red flag onto the field, indicating the challenge to the referees. This red flag was originally the "backup plan" if the pager were to fail, but over time proved to be prompter and more popular, as it showed the immediate and visual intent of the coach to ask for a review rather than a silent pager request without a visual indicator.
The referee has up to 90 seconds to watch the instant replay of the play and decide if the original call was correct. The referee must see "incontrovertible visual evidence" that the original call was incorrect for a call to be overturned. If the challenge fails, the original ruling stands, and the challenging team is charged with a timeout. If the challenge overrules the previous call, the call is reversed; should there have been an official score change, the score will be changed again, resulting in the original score and with no loss of a timeout.
Initially, the referee departed the field of play to a covered booth equipped with a CRT television monitor to consult the video replays. Over time, the equipment was upgraded, first to high-definition, then to touch screen monitors under the hood. Eventually the booth was abandoned in favor of portable Microsoft Surface tablets held by an assistant.
Because of the limited number of challenges, and the possible penalty of a lost timeout, coaches typically reserve their challenges for key plays. A questionable call may not be challenged once the next play is underway, so coaches may be forced to make a quick decision without the benefit of seeing a replay on television or on the stadium screen. If a questionable call is made in favor of the offense, then the offense will often line up and snap the ball quickly to prevent the opposing coach from challenging the call. Often players on the field will signal to the coach if they believe the play should be challenged.
