Goal-line technology explained: how it knows the ball crossed

"Did the whole ball cross the line?" used to be football's most agonising question. Goal-line technology answers it instantly and objectively. Here's how.

The rule it serves

A goal counts only when the whole of the ball has crossed the whole of the goal line, between the posts and under the bar. Just being on the line — even mostly over it — isn't a goal. For decades that exact moment was left to the human eye, often from a bad angle.

How the technology works

Goal-line technology (GLT) uses a set of high-speed cameras trained on each goal (some systems use magnetic fields instead). Software tracks the ball in three dimensions, and the instant the entire ball passes the line, it sends an encrypted signal — usually the word "GOAL" — to a watch on the referee's wrist within about one second.

The decision is automatic and final: there's no replay to interpret, just a yes or no.

How it's different from VAR

This is a common mix-up:

• Goal-line technology answers one binary question — did the ball cross the line? — automatically and instantly.
• VAR is a team of officials reviewing subjective match-changing decisions (fouls, offsides in the build-up, red cards) and advising the referee.

GLT needs no human judgment; VAR is all about judgment.

Why it was introduced

After several high-profile "ghost goals" — and goals wrongly disallowed — football adopted GLT to remove that specific injustice. It has been used at the World Cup and in major leagues since the mid-2010s, and ball-over-line controversies have all but disappeared.

The takeaway

Goal-line technology is the quiet success story of football tech: invisible until it's needed, instant when it is, and almost never argued with. Follow goals as they're confirmed in our live match centre.

FAQ

How accurate is goal-line technology?

Systems approved by FIFA must locate the ball to within a few millimetres, far beyond what any human eye or TV angle can judge. The referee receives the signal on their watch within about one second, so play barely pauses.

Do all leagues use goal-line technology?

No. Installation and running costs are significant, so it's mainly found in top divisions and major international tournaments. Many smaller leagues and lower divisions still rely on the officials — and, where available, VAR reviews — for ball-over-the-line calls.

Has goal-line technology ever failed?

Very rarely, but yes. The best-known case came in England in 2020, when the system gave no signal after the ball was carried over the line because the players' bodies blocked all the cameras' views. Incidents like that are the exception; across thousands of matches the technology has been overwhelmingly reliable.

Is goal-line technology the same as semi-automated offside?

No — they are separate systems. Goal-line technology answers only whether the ball fully crossed the goal line, while semi-automated offside uses limb-tracking cameras to help VAR judge offside positions. Both automate a factual question, but they use different setups and serve different laws.

Can players or managers ask for a goal-line review?

There's nothing to review — the decision is automatic. The signal goes straight to the referee's watch the moment the whole ball crosses the line, with no appeal system and no human interpretation involved, which is exactly why it causes so little controversy.