Goal-Line Technology

GLT stands for Goal-Line Technology: an approved camera-based or magnetic-field system whose only job is to say whether the whole of the ball has passed over the goal line.

GLT answers one binary question: has the whole of the ball passed over the goal line, between the posts and under the crossbar?

Hawk-Eye, a UK system, points seven high-speed cameras at each goal and triangulates the ball's centre in three dimensions. No chip, no sensor in the ball.

GoalControl is a German company from Wurselen. Its GoalControl-4D system was FIFA's choice for the 2013 Confederations Cup and the 2014 World Cup.

The signal is deliberately simple and private to the officials: the watch vibrates and shows the word GOAL, and the referee acts on it.

Hurst's shot hit the underside of the crossbar and bounced down on or near the line. The goal was given, but the human eye could not settle it - exactly the situation GLT was later built for.

Lampard's shot dropped a metre behind the line and bounced out. Neither the referee nor the assistant saw it, England were denied an equaliser, and FIFA's resistance to goal-line technology collapsed within two years.

GoalRef and Cairos put a passive chip inside the ball and weave thin coils around the goal frame. When the chip passes through the magnetic field the change is detected. It needs a special ball, which is why camera systems became the norm.

GLT watches the line continuously and fires by itself within a second; VAR must be initiated and covers four categories of decision.

Law 10 requires the whole of the ball to pass over the whole width of the goal line. If any sliver of the ball still overhangs the line, seen from above, it is not a goal - and GLT stays silent.

The Lampard incident (2010) created the pressure, IFAB approved GLT in July 2012, it debuted that December at the Club World Cup, and the Premier League installed it for 2013/14.

The FIFA quality standard, written into the IFAB approval, allows a maximum error of 3 cm on the ball's position. That is a fraction of the ball's own diameter, so a genuine 'on the line' case cannot be misread.

The Laws demand confirmation within one second, which lets the referee award the goal in real time rather than stopping the game for a review.

Seven high-speed cameras per goal, mounted in the roof and on the gantry. The overlap is deliberate: if players block some views, the rest can still fix the ball in three dimensions.

Fourteen: seven per goal, two goals. GoalControl used the same seven-per-goal architecture as Hawk-Eye at the 2014 World Cup.

Camera systems track a completely normal match ball - that is their main practical advantage. Only magnetic-field systems such as GoalRef need a special ball with a chip inside.

The Premier League installed Hawk-Eye in all 20 grounds for 2013/14, the first season after IFAB approval and the first top-flight league in Europe to do it.

The Bundesliga clubs voted GLT in for 2015/16 and installed Hawk-Eye - two seasons behind the Premier League, after an earlier vote had rejected it on cost.

Lines may be no more than 12 cm (5 inches) wide, and the ball must pass over the whole width of it.

Two: GoalControl-4D in Brazil in 2014, then Hawk-Eye in Russia in 2018 and Qatar in 2022. Both are camera systems with seven cameras per goal.

GLT is an aid, not a judge: the watch supplies the fact, and the referee applies the Law and awards the goal himself.

The Laws state the indication must be communicated only to the match officials, through their watches. Graphics for television and the big screen are produced separately, after the decision.

GLT never waits to be asked. It watches the goalmouth continuously and fires the moment the whole ball is over. That is its whole design difference from VAR.

Football has no challenge system. The GLT reading is treated as fact; a captain may ask the referee about it, but sustained protest simply earns a caution for dissent.

Goal-line technology assists a decision that belongs to the officials, so its failure removes the help rather than the decision: the assistant referee judges the line as he did before the system existed.

A system is approved in principle by IFAB, but every individual installation must then be tested and licensed in the ground itself under the FIFA Quality Programme before it may be used in a match.

Law 5 puts the pre-match test on the referee; a failed test means the match is played without GLT and the organiser is told afterwards.

AARs are the human answer to the same problem: an extra official beside each goal, judging the line by eye. UEFA used them in the Champions League and Europa League before technology took over.

The one-second signal exists so the referee can act immediately, before play develops any further. Waiting would leave a goal unawarded while the game runs on.

The assistant still watches the line and still signals; GLT is a second, more precise source of the same fact, and the fallback if it drops out.

GLT reports one physical fact and nothing else: the ball was wholly over. Whether that crossing counts as a goal is a separate legal question for the officials and the VAR.

The three geometric conditions of a goal - whole ball over, between the posts, under the bar - are precisely what GLT measures. Offences anywhere in the move are not its business at all.

Every camera is aimed at a goalmouth. The touchlines are 100 metres away from that field of view and remain the assistant referee's responsibility.

A goal is scored the instant the whole ball is over the line; what the ball does afterwards changes nothing, and GLT captures that instant.

'Wholly over' means wholly; a ball 90 per cent across is not a goal, and the system holds that line to within 3 cm.

GLT follows the ball, never the players. Goalkeeper encroachment at a penalty is judged by the assistant referee and, in competitions that use it, by the VAR.

A goal cannot be scored directly from a throw-in. GLT will still record the ball crossing, because that is all it can do - but the referee applies the Law and awards a goal kick.

The system has no idea whether a striker, a defender or the referee's shin sent the ball over. Attribution of the goal is entirely a human matter.

The system models the goal as a three-dimensional frame. A ball that flies over the bar or outside a post has not entered that frame, so no signal is sent.

GLT was right that the ball crossed; the VAR is right that the crossing was unlawful, so the offside in the build-up cancels the goal.

The whole point of a 3 cm system is that it beats the naked eye at 30 metres. The referee accepts the reading and awards the goal; there is no mechanism for over-ruling it by opinion.

Speed is what makes GLT invisible to the spectator. Because the answer arrives inside a second, there is no pause, no huddle and no screen check - the game simply carries on with the correct score.

GLT is optional and venue-specific. Most matches in the world are still played without it, and the referee and assistant judge the line exactly as they always did.

Use of GLT is set by the competition, not by the teams or the officials on the day. Once a licensed system is installed, it runs for the whole match.

Redundancy is the reason for seven cameras rather than two. Several views can be lost in a goalmouth scramble and the remaining ones still triangulate the ball to within the tolerance.

GLT fails silent, never guessing; if it cannot see the ball it sends nothing and the referee is back to eyes and the officiating team.

Since 2012 there has been no equivalent of Hurst or Lampard in a GLT-equipped match. The one type of error that used to be argued about for decades is simply gone.

GLT does not care who put the ball there or how: whole ball over the line, between the posts, under the bar is a goal, here credited as an own goal.

The watch is only a receiver, and the whole officiating team wears one, so the system keeps working even if the referee's own watch dies.

The crossing was real; the goal is not. Scoring with the hand or arm, deliberate or not, invalidates the goal, and GLT has no opinion on that.

Lampard's disallowed equaliser in Bloemfontein was replayed worldwide within minutes. FIFA, which had opposed technology for years, reopened the question and IFAB approved GLT two years later.

England v West Germany at Wembley, extra time. Hurst's shot came down off the underside of the bar and the goal was given after the referee consulted his linesman - the most argued-about goal in the game's history.

The 1966 goal was given on the linesman's word; a 1996 Oxford reconstruction later concluded the ball fell short of wholly crossing the line.

GLT debuted at the 2012 Club World Cup, GoalControl-4D covered the 2014 World Cup, the Premier League had already installed Hawk-Eye for 2013/14, and Hawk-Eye then became the default worldwide.

GoalControl-4D, chosen by FIFA after the Confederations Cup trial. It confirmed France's goal against Honduras in Porto Alegre - the first goal awarded by technology at a World Cup.

England went first, for 2013/14. The Bundesliga followed in 2015/16, Serie A in 2015/16 and La Liga considerably later - cost, not doubt about accuracy, was the usual reason for waiting.

Hawk-Eye, the British company already known from tennis and cricket, won the Premier League contract and installed cameras at all 20 grounds for 2013/14.

Pedro Mendes shot from the halfway line at Old Trafford; Carroll fumbled it a metre behind his own goal line and scooped it out. No goal was given, and the clip became a standard exhibit in the case for GLT.

UEFA backed the human option: an extra official beside each goal, judging the line by eye, before technology took over.

GoalControl had the 2014 World Cup, but Hawk-Eye took the leagues and then the tournaments, supplying GLT at the 2018 and 2022 World Cups. It is now the default provider worldwide.

GLT is a property of the stadium, not of the competition entry. One leg of a tie can be played with it and the other without, and that is accepted.

The system reports only when it can establish that the whole ball crossed; if too much of its view is blocked it stays silent rather than guessing.

Law 5 requires the pre-match test; if it fails, GLT may not be used, the match is played as a normal match, and the organiser is informed afterwards.

The goal was scored the moment the whole ball passed the line. Anything that happens to the ball inside the goal is irrelevant, and GLT has already signalled.

Where the keeper's body is has nothing to do with it: the Law is about the whole of the ball, and part-over is no goal.

The ball was dead before it crossed, so there was nothing to score with. GLT will still register the crossing, which is a good reminder that the watch reports physics, not law.

Silence from GLT is not evidence of no goal when the system could not see the ball. The referee falls back on the officiating team, exactly as in a match with no technology.

A goal may be scored directly from a goal kick, but only against the opponents. GLT confirms the crossing; the Law allows the goal.

A half ends when the referee blows, not when the clock passes the added minutes. If the ball is wholly over before that whistle, the goal counts.

A licensed installation is tested before the match and its reading is treated as fact. Protests, from the crowd or the club, have no standing in the Laws.

GLT: no initiation, one binary output, one second. VAR: initiated, four categories of decision, a check and possibly a review.

The AAR and GLT answer the same question. The difference is that a human standing beside the post is still estimating, while the cameras deliver a measurement to within 3 cm.

Both are camera systems, both use seven cameras per goal, both must meet the same 3 cm and one-second standard. The choice between them is commercial, not technical.

Both signal the same watch to the same standard. GoalRef and Cairos need a chipped ball and coils around the goal; Hawk-Eye and GoalControl read an ordinary ball with cameras - which is why they won.

DRS is a challenge system: the players spend reviews. Football chose the opposite philosophy for the goal line - the technology runs by itself and nobody gets to spend anything.

One narrow class of refereeing error has effectively been engineered out of the sport. That is a smaller claim than VAR makes, and it is the reason GLT is uncontroversial while VAR is not.

GLT is a wrist buzz and the word GOAL - no conversation needed. VAR is a voice in the earpiece and, for a review, a trip to the monitor.

SAOT does for the offside line what GLT does for the goal line: it turns a judgement of position into a measurement. The difference is that SAOT reports to the VAR, while GLT goes straight to the referee's wrist.

Three centimetres, against a ball 22 cm across, a human judging a bouncing ball at the far post is out by far more than that.

GLT was approved in 2012 and used from that December; VAR was only trialled from 2016 and written into the Laws in 2018.

GLT reported the crossing correctly, but the referee is not part of the game, so Law 9 restarts with a drop ball instead of a goal.

Silence from a working system is an answer: the ball was not wholly over. There is nothing to review and no reason to stop the game.

The ball crossed, so GLT was right; the goal was unlawful, so it does not stand, and the restart is a direct free kick for the foul.

The system saw the ball and did not signal, so the ball was not wholly over. Play continues; persistent surrounding of the referee can of course be dealt with later.

The match reverts to pre-2012 officiating. Goals already awarded stand, and the referee reports the failure to the competition afterwards.

This is the exact scenario GLT exists for. The goal was scored at the instant the ball was wholly over; the keeper's recovery is theatre.

The whole of the ball must cross the whole of the line, so most of it over is no goal; deliberate handling that denied a goal brings a penalty and a red card.

The reading is not negotiable, and dissent by word or action is a cautionable offence. Arguing with the watch is the quickest yellow card in football.

A goal may be scored directly from a corner kick against the opponents. GLT confirms the ball was wholly over; nothing in the Law stops the goal.

Where there is no technology, the extra official beside the goal is exactly the evidence the referee has. The AAR is a match official and the referee acts on the signal.

GLT changes how a fact is established, never what the Law says. A goal is still the whole ball over the line; only the accuracy of the judgement drops.

The standard is a confirmation within one second; 0.8 seconds is inside it, fast enough that the referee stops play before the game has moved on.

Seven cameras per goal, aimed at the goalmouth. The system is blind to the rest of the pitch by design - the touchline is still a human decision.

Only the geometric one. GLT would have measured the bounce off the bar in a second, and settled a fifty-year argument - but it would have had nothing to say about anything else in the move.

The crossing is measured and final. The lawfulness of the move is not - an offside, a handball or a foul before the shot is the one route by which the goal can still fall.

GoalRef is the magnetic-field system: a chip in the ball, coils around the goal. The camera systems read a standard match ball, which is a large part of why they prevailed.

A league cannot use technology the Laws do not permit; IFAB opened the door in July 2012, and the Premier League followed the next season.

GLT informs the referee; it does not bind him when it is silent because it could not see. Law 5 leaves the decision with the referee, and a goal he is sure of can be given.

A size 5 ball is about 22 cm across, so a 3 cm tolerance is roughly a seventh of it.

It is a geometry problem no human is placed to solve: a ball moving at speed, on a line 20 or 30 metres away, often hidden by bodies. That, and only that, is what GLT was built to fix.