The Video Assistant Referee (VAR) system will be used in competitive English football for the first time on Monday night when Brighton host Crystal Palace in the FA Cup third round.
Here, we look at the key issues regarding VAR.
What decisions can it be used for?
The referee can opt to use VAR on decisions concerning the awarding of goals, penalty kicks, the issuing of straight red cards and cases of mistaken identity. The referee can request assistance with these decisions or it can be recommended by the video officials, but the referee on the pitch has the final say after being talked through what the footage shows.
Where has it been used?
It has been in use all season in Serie A and the Bundesliga, among 15 leagues worldwide to test the technology.
Will it be used at the World Cup this summer?
FIFA president Gianni Infantino is certainly keen for that to happen. The game's law-making body, the International Football Association Board (IFAB) will make a final ruling when it gathers for its annual general meeting in March.
Have there been any teething problems?
There have been concerns over the delays caused by VAR referrals, with Juventus coach Massimiliano Allegri complaining that the game was "turning into baseball". There was also an embarrassing incident in MLS in September when the decision to send off New England Revolution midfielder Xavier Kouassi using VAR was overturned on appeal.
How regularly has it been used?
ESPN reported there were 309 incidents reviewed using VAR in Serie A up to October 30. Of those, 288 backed the referee's initial call and 21 decisions were overturned.
Can players, managers or others call for VAR to be used?
Players risk a booking if they attempt to influence any official to use VAR and managers or other non-playing club staff risk being sent to the stand if they do the same, or encroach on the area where the referee is reviewing footage.