If it proves successful, the technology is set to be introduced to the Premier League before the 2024/25 season is out.
The FA explained the change, saying: "Semi-automated offside technology will provide more efficient placement of the virtual offside line, based on optical player tracking, and produce virtual graphics to ensure an enhanced in-stadium and broadcast experience for supporters.
"The operation of semi-automated offside technology does not change the accuracy of the decision making but enhances the speed and efficiency of the process."
In-stadium VAR announcements will also be made by the referees during the fifth-round games.