http://www.bbc.com/sport/football/43269186
Video assistant referees are set to be used at this year's World Cup in Russia after football's lawmakers voted to approve the technology.
VAR has been trialled in some domestic English cup games this season, and has been used in Germany and Italy.
The International Football Association Board (Ifab) "unanimously approved" its introduction on a permanent basis after a meeting in Zurich on Saturday.
Leagues and competitions must now apply to Ifab to implement the system.
Fifa president Gianni Infantino said a decision on whether VAR would be used at the World Cup will be taken at a meeting on 16 March.
"As of today, video assistant refereeing is part of football," he said.
"We hope and encourage a favourable decision in this respect because we are very positive about VAR."
One of the concerns over VAR is that those watching are uncertain about what is going on, but Fifa says it is working on a system that will provide information to the "giant screen operators as well as broadcasters and commentators" about the reason and outcome of a review.
"What is our idea (for the World Cup) is that after the final decision is taken by the referee on the pitch we would like to show in the stadium the selected replay that was used by the referee and VAR," said Johannes Holzmuller, head of Fifa football technology innovation.
'It's almost perfect'
Ifab is made up of world governing body Fifa and the Football Associations of England, Scotland, Wales and Northern Ireland.
Each FA has one vote to Fifa's four, with six votes required for a change in the laws.
Saturday's decision was made after Ifab was presented with the results of independent analysis conducted by Belgian university KU Leuven.
"I would say to the fans, players and coaches that it will have an impact, a positive impact," said Infantino. "That is what the results of the study show.
"From almost 1,000 live matches that were part of the experiment, the level of the accuracy increased from 93% to 99%. It's almost perfect."
Infantino says he was "pretty much against" the system until he "studied it".
"We have looked into all the details and benefits it can bring," he said.
"Of course, we need to speed up the reviews and the communication to the referees that are applying it but also for the general public."
The Premier League is not expected to introduce VAR next season, and Uefa has already said it will not be used in the Champions League next season.
France's Ligue 1 is to introduce it from next season, while the Bundesliga will decide on 22 March whether to use VAR.
"In all my discussions with people in the Premier League, they can all see benefit of VAR," said Football Association chief executive Martin Glenn.
"If they do choose to not implement it then it won't be a fundamental rejection of VAR - it will be a case of giving it more time."
Ifab has also approved allowing teams to use an "additional" substitute in extra time of matches.
'Minimum interference - maximum benefit'
Ifab said the "philosophy" of VARs is "minimum interference - maximum benefit" with the intention of reducing "unfairness caused by clear and obvious errors or serious missed incidents".
It added the incidents that referred to would be in relation to:
Goal/no goal
Penalty/no penalty
Direct red card (not second yellow card/caution)
Mistaken identity (when the referee cautions or sends off the wrong player)
VAR was first used at the Club World Cup in December 2016, and trialled in the 2017 Confederations Cup.
The system was described as "comical" and "embarrassing" after Tottenham's 6-1 FA Cup win over Rochdale on Wednesday, when a goal was disallowed and a converted penalty overturned.
Any domestic league or competition would have to adopt VAR protocols for every game.
On Friday, the Premier League it was "monitoring closely the video assistant referee trials being conducted in other competitions".
It added: "The evidence and learning provided by those trials will inform further discussions with our clubs later this season."
Video assistant referees are set to be used at this year's World Cup in Russia after football's lawmakers voted to approve the technology.
VAR has been trialled in some domestic English cup games this season, and has been used in Germany and Italy.
The International Football Association Board (Ifab) "unanimously approved" its introduction on a permanent basis after a meeting in Zurich on Saturday.
Leagues and competitions must now apply to Ifab to implement the system.
Fifa president Gianni Infantino said a decision on whether VAR would be used at the World Cup will be taken at a meeting on 16 March.
"As of today, video assistant refereeing is part of football," he said.
"We hope and encourage a favourable decision in this respect because we are very positive about VAR."
One of the concerns over VAR is that those watching are uncertain about what is going on, but Fifa says it is working on a system that will provide information to the "giant screen operators as well as broadcasters and commentators" about the reason and outcome of a review.
"What is our idea (for the World Cup) is that after the final decision is taken by the referee on the pitch we would like to show in the stadium the selected replay that was used by the referee and VAR," said Johannes Holzmuller, head of Fifa football technology innovation.
'It's almost perfect'
Ifab is made up of world governing body Fifa and the Football Associations of England, Scotland, Wales and Northern Ireland.
Each FA has one vote to Fifa's four, with six votes required for a change in the laws.
Saturday's decision was made after Ifab was presented with the results of independent analysis conducted by Belgian university KU Leuven.
"I would say to the fans, players and coaches that it will have an impact, a positive impact," said Infantino. "That is what the results of the study show.
"From almost 1,000 live matches that were part of the experiment, the level of the accuracy increased from 93% to 99%. It's almost perfect."
Infantino says he was "pretty much against" the system until he "studied it".
"We have looked into all the details and benefits it can bring," he said.
"Of course, we need to speed up the reviews and the communication to the referees that are applying it but also for the general public."
The Premier League is not expected to introduce VAR next season, and Uefa has already said it will not be used in the Champions League next season.
France's Ligue 1 is to introduce it from next season, while the Bundesliga will decide on 22 March whether to use VAR.
"In all my discussions with people in the Premier League, they can all see benefit of VAR," said Football Association chief executive Martin Glenn.
"If they do choose to not implement it then it won't be a fundamental rejection of VAR - it will be a case of giving it more time."
Ifab has also approved allowing teams to use an "additional" substitute in extra time of matches.
'Minimum interference - maximum benefit'
Ifab said the "philosophy" of VARs is "minimum interference - maximum benefit" with the intention of reducing "unfairness caused by clear and obvious errors or serious missed incidents".
It added the incidents that referred to would be in relation to:
Goal/no goal
Penalty/no penalty
Direct red card (not second yellow card/caution)
Mistaken identity (when the referee cautions or sends off the wrong player)
VAR was first used at the Club World Cup in December 2016, and trialled in the 2017 Confederations Cup.
The system was described as "comical" and "embarrassing" after Tottenham's 6-1 FA Cup win over Rochdale on Wednesday, when a goal was disallowed and a converted penalty overturned.
Any domestic league or competition would have to adopt VAR protocols for every game.
On Friday, the Premier League it was "monitoring closely the video assistant referee trials being conducted in other competitions".
It added: "The evidence and learning provided by those trials will inform further discussions with our clubs later this season."
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