FIFA confirms video assistants will be used in World Cup Finals
The system allows referees decisions to be over-ruled when replays show a clear and obvious error. The International Football Association Board had the move at a meeting earlier this month.
"VAR really helps referees," said FIFA President Gianni Infantino. "And it will help us have more transparent and fairer football, which is what we want."
Critics say that VAR interrupts the rhythm of matches.
FIFA also confirmed a fourth substitute will be allowed in matches that go to extra time.