Which World Cup was the first to use goal-line technology?

Whether the whole of the ball had crossed the goal line was, for most of football's history, a judgement call. Referees and linesmen made it in real time, often from awkward angles, and they sometimes got it wrong. Some of the most famous moments in World Cup history involve disputed goal-line calls — the most famous of all being Geoff Hurst's second goal in the 1966 final. By the early 2000s, with high-definition cameras and slow-motion replays available to fans at home, those judgement calls were under constant scrutiny. The sport eventually had to decide whether to keep relying on the human eye or to bring in technology.

A specific match at the 2010 World Cup made the case impossible to ignore. In a round-of-16 game between England and Germany, England's Frank Lampard struck a shot that hit the underside of the crossbar, bounced clearly down behind the line, and bounced back out. Replays showed it was an obvious goal. The referee did not see it, and the goal was not given. Germany won the match 4–1. Public criticism of the missed call was loud and global, and within a few years FIFA had committed to introducing a system that would take that exact decision out of human hands.

The system used at the World Cup uses multiple high-speed cameras around each goal, tracking the ball from every angle. When the whole ball crosses the goal line, the system processes the camera data within a fraction of a second and sends a signal directly to a special watch the referee is wearing on their wrist. The watch vibrates and shows the word GOAL. From the referee's point of view it is almost instant: no waiting, no replay review, no debate. The whistle goes for a goal, exactly as it would in a clean conventional case.

The 2014 World Cup in Brazil was the first edition to put the system to use. The first goal it confirmed at a World Cup came in a group-stage match between France and Honduras. The shot crossed the line in a busy moment that the naked eye could easily have missed; the watch confirmed it within seconds, the referee gave the goal, and the technology had its debut. Since then, goal-line technology has become standard at the World Cup and at all major club competitions that can afford it.

Goal-line technology is one of the quiet revolutions of modern football. It does not change anything when a goal is obvious; it changes everything when a goal is too close to call. By making that single judgement automatic, the system removed an entire category of controversy from the game. The Lampard moment that drove its adoption has not been repeated at any World Cup since.

This article was written using information from Wikipedia.