Instant replay in American and Canadian football In American and Canadian football , instant replay is a method of reviewing a play using cameras at various angles to determine the accuracy of the initial call of the official s . 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 . 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 . Examples of plays that cannot be reviewed – even if replays would show an incorrect call was made – include a quarterback fumble recovered by the defensive team that is ruled an incomplete pass and thus whistled dead , or a player ruled downed or out of bounds when in fact he was not . American and Canadian football leagues vary in their application and use of instant replay review . By league . National Football League . The National Football League first adopted a limited Instant Replay system in 1986 , though the current system began in 1999 , bringing in the opportunity to " challenge " on - field calls of plays . The current system mirrors a system used by the now defunct USFL in 1985 . Each coach is allowed two opportunities per game to make a " coach ' s challenge " . Before the 2004 NFL season , the instant replay rule was slightly changed to allow a third challenge if both of the original two challenges were successful . A challenge can only be made on certain reviewable calls on plays that " initiated " before the two minute warning and only when a team has at least one time - out 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 coaches now throw 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 it has become the more popular option among NFL coaches to signal a replay request . The referee has 60 seconds to watch the instant replay of the play and decide if the original call was correct . The referee must see " incontrovertible visual evidence " 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 . 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 . During a scoring play ( starting in 2011 ) , turnovers ( starting in 2012 ) , or after the two - minute warning of each half , and in overtime , reviews can only take place if the replay assistant , who sits in the press box and monitors the network broadcast of the game , determines that a play needs review ; coaches may not challenge during these times . In those cases , the replay assistant will contact the referee by a specialized electronic pager with a vibrating alert . If a review takes place during that time while the clock is running , the clock will stop for the review , and then it will start running once the ball is set and ready for play . Starting with the 2010 season , any reviews with the clock running inside one minute will have a 10 second rundown , which can be voided if either team uses a timeout . One concern about replay that was addressed some years ago was the situation where a coach would seek a review of a non - challengeable call ( such as being forced out of bounds , or in some cases to challenge a runner down by contact ) . Before the rule was clarified , a team would lose the challenge and a time - out . The current rule does not penalize a team in such a case , provided the rule is not abused or taken advantage of . The NFL replay system currently only covers the following situations : If a play is overturned , the official is also responsible for making any related revisions to the game clock if applicable , especially in late , game - ending situation . For instance , if a player makes a reception and runs a long distance , several seconds may run off the game clock . If the play is challenged and the catch overturned , the game clock would be reset to have stopped at the moment of incompletion ( presumably adding time back to the clock ) . Note that the spot of the ball may be challenged in certain cases . In such cases , a decision to respot the football is not enough to win the challenge ; only when the ball is respotted " and " the ruling on the field is reversed by remeasurement is the challenging team not charged a timeout . Some unusual , and confusing sequences of events can occur during replay stoppages , and most have been addressed through rules clarifications . For instance , if a team commits a delay of game penalty ( before the snap ) , the opposing team still has the opportunity to challenge , provided it is done before the ensuing snap . Also , inside the two minute warning , if a team calls a timeout in the normal course of play , but the replay assistant calls for a challenge of that play , the initial timeout is ignored and restored in favor of the replay stoppage . History . The current replay system replaced a previous system used during from 1986 through 1992 , when a procedure similar to that of college football was used . In 1987 commissioner Pete Rozelle saved the system for another season , in 1988 Pittsburgh Steelers owner Dan Rooney saved it . From before 1986 , and from 1993 to 1998 , no replay system was used . While there is occasional controversy over the appropriateness of overturned calls , the system is generally accepted as an effective and necessary way to ensure a fair game . NCAA football . In 2006 , the NCAA Football Rules Committee enacted instant replay guidelines and added them to the football playing rules . For games involving two schools from the same conference , league policy determines whether replay will be used . For non - conference games , the home team makes the determination . Plays involving the sideline , goal line , end zone and end line , as well as other detectable situations , are reviewable ( e . g . , fumble / no fumble , pass complete / incomplete , touchdown / no touchdown , runner down / not down , player or ball inbounds / out of bounds , clock adjustments ) . Most fouls ( e . g . , holding , offside , pass interference ) are not reviewable , except that in 2006 , illegal forward passes , handoffs and punts from beyond the line of scrimmage , and too many players on the field are reviewable and the foul may be called after replay review . Also , while the foul of pass interference is not reviewable , it can be overturned on review based on touching of the pass . By rule , pass interference cannot apply if a pass has been touched by any player before the foul occurs , and the touching of a pass is a reviewable play at its conclusion from a secure booth in the press box . Most plays are routine and the game continues without interruption . If , however , the following criteria are met , the Replay Official may interrupt the contest by paging the game officials to stop the game before the next play starts . The criteria are : Once per game , each head coach may also call a timeout and challenge the ruling on the previous play before the next play starts . A coach must have at least one timeout remaining in order to challenge ( teams receive three timeouts per half ) . If the challenge is successful and the on - field ruling is overturned , the team keeps its timeout and is allowed only one more challenge . If unsuccessful , the team loses its timeout and is allowed no more challenges . After reviewing the play from available video angles , the Replay Official decides if the call should be upheld or overturned . If the call is overturned , the Replay Official provides the proper information to restart the game , such as the team in possession , the yardline where the ball should be placed , the correct down and distance , and the correct time on the stadium clock . Should there have been an official score change , the score will be changed again , resulting in the original score . College football instant replay was started by the Big Ten Conference in the 2004 season because of what happened in the 2001 Michigan vs . Michigan State football game , when reviews were used experimentally in the Big Ten Conference only . In the 2005 season , all conferences were allowed to use instant replay . Among Division I Football Bowl Subdivision ( see Division I - A ) conferences , the Atlantic Coast Conference , Big East , Big Ten , Big 12 , Conference USA , MAC , Mountain West Conference , Pac - 10 , and SEC used replay in 2005 . The Sun Belt and Western Athletic did not . In 2005 , the Big 12 initially sought to provide field monitors which would allow the on - field referee to assist the replay official ; however , by the first game of the season , they decided to only provide equipment to the instant replay booth . Conference USA used a similar system , but the on - field referee made the decision after viewing a TV monitor on the sideline . The Mountain West Conference was the only league to allow a head coach ' s challenge . Each head coach got one challenge per half . If the call was overturned , the challenging coach kept his timeout and got a second challenge for that half . If not , the challenging coach lost one of his three timeouts for the half . No more than two challenges per half per coach were allowed . There is not currently an Instant Replay equipment standard , each conference must choose ( and purchase ) its own equipment . Therefore , systems are quite disparate : they can be as complex as the high - tech custom systems similar as those used in the NFL to as simple as several large screens hooked to a digital video recorder using the direct - to - air feed of the broadcasting entity televising the game or a venue ' s internal coverage unit . In 2005 , the Big Ten , MAC , and SEC only allowed broadcast video ( for games that are televised ) to be used to determine the correct call . The other conferences allowed broadcast video and scoreboard video . Most conferences provided video equipment for games that were not televised . Instant replay was used in post - season games for the first time in the 2005 season . It was used in all 28 bowl game s as well as the Division I Football Championship Subdivision ( FCS , née 1 - AA ) , Division II and Division III national championship playoff games . Canadian Football League . The Canadian Football League board of governors approved the use of instant replay starting in 2006 . The CFL system appears to be modeled largely on the NFL ' s , although some differences have been incorporated to accommodate differences between the two codes :