For most of tennis history, line judges called whether the ball was in or out. At a growing number of events, cameras now do the job in real time.
How it works
Live electronic line calling uses a network of cameras around the court to track the ball. When a shot lands out, a recorded voice call plays instantly, so there are no challenges and no delays.
Who uses it
The Australian Open and US Open switched to electronic calls in 2021. The ATP introduced it across all its tour events from 2025, and Wimbledon replaced its line judges with the system in 2025, ending a tradition that went back to the first championships in 1877.
What about clay?
Clay events often still rely on umpires checking the mark the ball leaves on the court, although some have started using electronic systems too.
