Semi-automated offside, VAR and goal-line technology explained

Three systems, three different jobs

Refereeing technology is often discussed as one thing. In practice each system has a narrow, defined role under the Laws of the Game, and confusing them leads to wrong expectations about what technology can decide.

Goal-line technology: the one fully automatic decision

Goal-line technology is the only system that gives a decision directly. It answers a single factual question, whether the whole ball has crossed the line between the posts and under the crossbar, and sends a vibration and visual signal to the referee's watch within one second. Only match officials receive the signal.

• Camera-based systems use several high-speed cameras around each goal to triangulate the ball's position.
• Magnetic-field systems use a ball with an embedded sensor and fields generated around the goal frame.
• Licensing. Systems are tested under the FIFA Quality Programme, every stadium installation must pass a final test, and the referee checks that the system works before each match.

In England, the Premier League introduced goal-line technology for the 2013/14 season, and the 2014 World Cup was the first men's World Cup to use it. The Laws permit it but do not require it, and the cost of certified installation per stadium keeps it out of amateur football.

How does VAR work?

VAR is a team of video match officials who watch every match situation, but may only intervene in specific categories: goals and offences leading to a goal, penalty decisions, direct red cards, and mistaken identity when a card is given. The threshold is a clear and obvious error, or a serious missed incident. The on-field referee always makes the final decision, either by accepting the VAR's factual information or by reviewing footage at the pitchside monitor.

The IFAB's annual meeting in February 2026 extended the scope where there is clear evidence: VAR may review a sending-off that results from a clearly incorrect second yellow card, cases where the wrong team is penalised and a card goes to the wrong player, and, if the competition chooses, a clearly incorrectly awarded corner kick, provided the check is immediate and does not delay the restart. The 2026/27 Laws also allow referees to wear chest- or head-mounted body cameras as a competition option, after their use at the 2025 FIFA Club World Cup.

Semi-automated offside technology, step by step

Offside is a geometry problem at a precise moment: where the attacker's relevant body parts are, relative to the second-last defender and the ball, at the instant a team-mate plays the ball. Standard VAR solved it by stopping the video at the kick frame and drawing lines by hand, which was slow and depended on the frame chosen.

1. Tracking. For the 2022 World Cup, FIFA described 12 dedicated cameras under the stadium roof tracking up to 29 data points on each player, 50 times per second.
2. Kick point. A sensor in the centre of the match ball sent data 500 times per second, identifying the exact moment the ball was played.
3. Alert. When an attacker in an offside position receives the ball, the system alerts the video officials.
4. Validation. The video officials check the proposed decision, including whether the attacker actually became involved in play, and inform the referee, who confirms it.
5. Communication. The same data generates a 3D animation shown on stadium screens and to broadcasters.

UEFA first used SAOT at the 2022 UEFA Super Cup in Helsinki and in the Champions League from the 2022/23 group stage. The Premier League introduced it in April 2025, first using it in Matchweek 32 on 12 April, with a system based on optical player tracking. At the 2026 World Cup, FIFA used an advanced version that sends clear positional offsides directly to the on-pitch assistant referees, with every player 3D-scanned for more accurate avatars, and 16 optical tracking cameras in each stadium.

Limits that technology does not remove

• Interpretation stays human. SAOT measures position. Whether an attacker interfered with an opponent or the play is a judgement, and the 2026 advanced system still covers positional offside only.
• Measurement has tolerances. Camera frame rates, body-point estimation and the kick-point moment all carry small uncertainties; very tight calls are decided within the system's precision, not with absolute certainty.
• Delays and flow. Even fast checks interrupt celebration and rhythm; competitions trade some flow for accuracy.
• Cost and infrastructure. Calibrated cameras, connected balls, video operation rooms and trained officials are only feasible at professional level.

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What can reach amateur and youth football

The closest thing to video review for lower levels is Football Video Support (FVS), a FIFA-led trial in which coaches can challenge a decision and the referee reviews it at a pitchside monitor using the available camera angles. It was first used at the 2021 FIFA Futsal World Cup, has since been used at FIFA youth and women's youth tournaments, and has been announced by some national competitions. Each team has a limited number of challenges, and an unsuccessful one uses it up. It needs cameras, a replay operator and trained officials, so it is still a professional or semi-professional tool.

• No video review in grassroots matches. Under the Laws, decisions cannot be changed on the basis of a parent's phone video; video review exists only in authorised competitions following the official protocols.
• Referee development. Footage, used with consent and the safeguards set out in filming youth football and data protection, is valuable for referee mentors to review positioning and decisions with young officials.
• AI-assisted education. Tools that auto-clip incidents can help clubs and county referee groups build training clips; treat any automatic offside line from a single amateur camera as an illustration, not evidence.
• Behaviour first. Most grassroots refereeing problems are about respect and touchline behaviour, not accuracy. See respect the referee.

For coaches explaining the rules to young players and parents, the football rules guide for parents covers offside at each format.

Frequently asked questions