An electronic line judge is a device used in tennis to automatically detect where a ball has landed on the court. Attempts to revolutionize tennis officiating and the judging of calls in the sport began in the early 1970s and has resulted in the design, development and prototyping of several computerized, electronic line-judge devices. The methods have been based upon the use of pressure sensors, sensors to detect magnetized or electrically conductive tennis balls, infrared laser beams, and most recently video cameras.

The 2021 Australian Open was a Grand Slam tennis tournament that took place at Melbourne Park, on 8–21 February 2021. It was the 109th edition of the Australian Open, the 53rd in the Open Era, and the first Major tournament of the year. It was originally scheduled for 18–31 January 2021, but was postponed by three weeks to February due to the COVID-19 pandemic. The event was part of the 2021 ATP Tour and the 2021 WTA Tour.