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.