Goal-Line Technology: How Cameras Decide Goals

Goal-line technology (GLT) decides whether the whole ball has crossed the goal line, between the posts and under the crossbar. Cameras, or in some systems a chip in the ball and magnetic coils, track the ball, and when it is fully over the line a signal reaches the referee's watch within about a second. The referee is assisted by the system, not replaced by it.

The technology answers one question and nothing else. It does not rule on offside, fouls or handball, which is why the offside law and VAR still matter around every goal. Below, we explain how it works, why it arrived, and what the Laws require, with the match moments that prompted the change.

The short answer

The system works out whether the ball has completely crossed the line. FIFA's testing requirements set out four basics: it addresses only whether a goal was scored, it must be accurate, it must indicate a goal immediately (confirmed within one second), and it communicates only to the match officials, through a vibration and a visual alert on the referee's watch.

That narrow remit is deliberate. If a striker handled the ball in the build-up or was offside, the technology can still confirm the ball crossed the line, but the referee and, where it is used, VAR deal with the offence. GLT is not the same system as VAR.

Why the technology was introduced

In March 2010 FIFA and the International Football Association Board (IFAB) voted to drop the idea. That summer, at the World Cup, Frank Lampard's shot for England against Germany bounced off the crossbar and over the line, and the goal was not given. Sepp Blatter later said the discussion would be reopened.

Euro 2012 sharpened the debate. In Ukraine v England, replays showed Marko Devic's shot in the 62nd minute had crossed the line before John Terry cleared it. Blatter said that after that match the technology was 'no longer an alternative, but a necessity'.

In July 2012 IFAB amended the Laws to permit GLT. The Laws allow it but do not require it, and because of its expense it has been used only at the highest levels. UEFA president Michel Platini was opposed and preferred a system of five match officials, and individual associations could still decide not to use the technology.

How camera systems work

The best-known camera system is Hawk-Eye. As set up for the Premier League from the 2013/14 season, it uses seven cameras at each end of the stadium focused on the goals, most often mounted on the roof. Software processes the images to find the ball and separate it from everything that is not the ball, which lets the system locate it even when only a small part is visible.

The result goes to the referee's watch within a second, using an encrypted signal designed to be unaffected by interference. FIFA's requirement is a margin of error of plus or minus 3cm, and the Hawk-Eye system is said to beat that figure. Later installations may differ, and accounts vary on camera counts and accuracy figures, so no single figure is given here for every setup.

Viewers see something different. A broadcast replay is available within about 10 seconds, but it is not the signal the referee receives. For an interactive take on split-second judgement, see our Freeze Frame page.

The magnetic-field alternative

Not every system uses cameras. Cairos, another system tested in the process, used a chipped ball and a magnetic field. A passive chip sits inside the ball, and coils in the posts and crossbar create a field that detects when the ball crosses the line.

One account of this method says it works in poor visibility but needs a special ball. That account comes from a club-affiliated source, so treat the claim as its view rather than settled fact. The same account says camera systems need a clear line of sight and that margins of error can widen in crowded situations.

What the rules require

The rule itself is simple: the ball must pass completely over the goal line, between the posts and under the crossbar, while in play. Close calls are not decided by how much of the ball looks to be over the line. If any part is still above the line, there is no goal.

Law 1.11 permits GLT only where competition rules stipulate its use, so whether a match has it depends on the competition. The referee must test the system before kick-off and must not use one that is failing. Where VAR is authorised, goal or no-goal is a reviewable category, but it remains a separate system.

Technology also cannot rewrite the restart rules. If a referee deflects a pass into the goal, the result is a dropped ball under Law 9.1, not a goal. For other terms that crop up in these debates, our glossary of football terms helps.

Limits and open questions

A list of licensed installations dated September 2024 showed 144 stadiums, 135 using Hawk-Eye and 9 using Vieww. Current league-by-league coverage is not confirmed here, so check a competition's own rules before assuming GLT is used. No reliable figure for the cost of a system has been confirmed, so none is given.

Goal-line technology has addressed the ghost goal. The decisions around it, from offside to fouls, remain human, and the same tension between certainty and judgement runs through other moments, such as the psychology of penalty shootouts.