An explanation from the Premier League says "computer vision cameras" will be placed in every top-flight stadium this season.
"These cameras around the ground will track the ball as well as thousands of data points for each player and the ball," the Premier League adds.
"When a match-defining moment occurs, such as a penalty, a goal or a red card, the technology will track to see if any attacking player involved in the build-up to the incident was offside.
"If a player receives a ball in an offside position, the technology will send an alert to the officials in the VAR Hub.
"They will check that the point of contact with the ball and automated offside line have been correctly recorded. The VAR will then inform the on-field officials if an offside has been recorded."