In a recent Premier League game, Manchester United went 2-0 up when striker Marcus Rashford ran on to a pass and slotted the ball past Liverpool’s goalkeeper, Alisson Becker. The game was then held up briefly while the “video referee” checked whether Rashford was ahead of the last defender, Joe Gomez, when the pass was made. The difference between onside and offside – between goal or no goal – can be tiny:
