clock menu more-arrow no yes mobile

How the World Cup’s AI instant replay works

A new hyper-accurate technology and referees’ eternal quest for objectivity.

The most concise way to understand the offside rule is in the words of the Scott Fujita blog: an offside is the result of an attacking player getting closer to the opponent’s goal line than both the ball and the last defender. It’s a rule that sounds objective, but it has led to a lot of questionable calls, partly because it can only be judged from an individual perspective. Until now. Meet the new “semi-automated AI offsides technology” at the 2022 World Cup.

A sensor in the ball relays the position of the ball on the field 500 times a second. Twelve motion-tracking cameras mounted under the roof of the stadium use machine learning to track 29 points in players’ bodies. In other words, FIFA is mo-capping players, just without the funny gray suits. The system will alert referees when a player is offside.

This motion-tracking information will also be used to create an immediate 3D replay of the the offside event (or theoretically any other call) that will demonstrate why the call was made to both the audience and the referees. On the surface, this tech seems incredible for eliminating “bad” calls, but its precision will inevitably impact gameplay.

Check out the latest Vox video to learn more about how this system may change the sport.

You can find this video and all of Vox’s videos on YouTube.