Video Assistant Referee causes controversy every week in the Premier League, but how are decisions made, and are they correct?
After each matchday we take a look at the major incidents to examine and explain the process both in terms of VAR protocol and the Laws of the Game.
In this week's VAR Review: Exploring the reasons behind the missed red card for Everton's James Tarkowski, and explaining the offside claim on Liverpool's winning goal on Wednesday night. Plus, should Aston Villa and Brentford have been awarded penalties?
Liverpool 1-0 Everton
Possible red card: Serious foul play by Tarkowski
What happened: Everton defender James Tarkowski went to make a clearance from the edge of the area in the 11th minute and made high contact on Liverpool midfielder Alexis Mac Allister. Referee Sam Barrott produced a yellow card and it was checked for a possible red by the VAR, Paul Tierney.
VAR decision: No red card.
VAR review: Tarkowski came running in at speed and won the ball. As he moved his leg through, he caught Mac Allister on the calf with his studs in a swinging action. This ticked all the boxes for serious foul play -- a tackle or challenge that endangers the safety of an opponent or uses excessive force.
So why didn't the VAR intervene?