Today, Major League Soccer. Tomorrow, the world.

Despite purists who believe the beautiful game should never be sullied by video replay, it has arrived and isn’t going anywhere. Major League Soccer will start using it for every match, even the postseason, starting Saturday.

The Video Assistant Referee, VAR for short, was showcased on an international level during this summer’s Confederations Cup in Russia and the Under-20 World Cup in South Korea, with mixed results.

But MLS has been preparing for this moment for three years.

“The idea is minimum interference for maximum benefit,” said veteran referee Howard Webb, who is overseeing the league’s implementation of video replay. “We’re not trying to change the way the game is played. We’re trying to enhance it. We’re trying to make it fairer. ”

Australia’s top-flight A-League used a version of video review on trial earlier this year, and the South Korean K-League Classic began working with it in July.

At least two other top-tier leagues will add VAR. The German Bundesliga will debut video replay for the season opener between Bayern Munich and Bayer Leverkusen on Aug. 18. The Italian Serie A will also introduce its version after adding goal-line technology last season.

For now, all eyes are on MLS and how it rolls out the VAR protocol. The league has not stated its investment in video review.

“We’ve seen some really big players – and make no mistake about it MLS is a big player in the global soccer world – make the decision to take it on board, and undoubtedly we will be watched by the leagues that haven’t made the decision as well as the leagues that are doing it,” Webb said. “We are confident with our extensive preparation that what they’ll see will encourage them to do the same thing.”

Webb serves as manager of video assistant referee operations for the Professional Referee Organization, which oversees on-field officials in the U.S. and Canada. He’s got the credentials: He was a Premier League referee from 2003-14, and also worked the Champions League and World Cup finals in 2010. He also served as director of referees for the Saudi Arabian Football Federation.

Soccer’s rule-making body, the International Football Association Board, approved trials of video technology in March 2016. Internationally, live experiments are taking place in about 20 competitions this year, including the recent Confederations Cup, considered a test for the 2018 World Cup.

Implementation at the Confederations Cup drew criticism because of slow reviews that seemed to confuse players, coaches and fans. But FIFA concluded that video replay helped referees overturn six “game-changing decisions.” Calls made in 29 additional “major incidents” were confirmed correct on review.

“What fans have been waiting for over so many years is finally happening. This is a milestone tournament. Video Assistant Refereeing is the future of modern football.” FIFA President Gianni Infantino said.

It is expected that the IFAB will add video replay to the laws of the game within the next two years, and any competition meeting the requirements will be able to use it.

For the MLS program , a fifth member of the officiating crew – the Video Assistant Referee –will be at each MLS stadium and will monitor all video feeds of the game that are available, focusing on “potential clear and obvious errors or serious missed incidents” involving goals, penalty kicks, straight red cards and mistaken identity.

If a review is required, the VAR will alert the referee on the field, who will make a box gesture with his hands to indicate the VAR is examining a possible error. All final calls will lie with the head referee.