The Premier League spent two years testing a number of artificial intelligence-based semi-automated offside technology (SAOT) providers, and now it’s ready to be rolled out.

UEFA was first to introduce SAOT in the Champions League from the start of the 2022-23 season group stage, quickly followed by FIFA for the World Cup in Qatar.

SAOT made its belated debut in English football in the FA Cup fifth round on Feb. 28, 2025, featuring in the seven ties being played at Premier League grounds. After successful live trials, SOAT is being introduced into the Premier League for Matchweek 32, on April 12-14

What is this new technology, how does it work, and is it really any better?

Why did VAR offside need to change?

Long delays, perceived inaccuracies and a lack of confidence in the “crosshairs” system among fans, players and coaches. And that’s just for starters.

Scepticism also came from the poor visualisation of decisions, with lines placed on the pitch that cannot replace a person’s own perspective. A player may have looked onside, but the technology said they were offside. At other times, the lines were so close to each other it was hard to understand the outcome.

Selecting the exact moment the ball was touched by the passer could not be determined accurately because of the frame rate of TV cameras (50 frames per second).

The VAR also had to manually select the farthest forward point on both defender and attacker (or the ball if applicable) using “crosshairs,” which couldn’t be applied consistently or accurately. Then there was the time it would take to judge offside, in some cases up to five minutes for complex decisions.

Some grounds caused more trouble than others, too — especially Selhurst Park, where it took over four minutes to confirm a Crystal Palace goal earlier this season.

All in all, supporters didn’t really trust the process — not helped by a number of high-profile errors either.

In February 2023, the VAR failed to identify that a Brentford player was offside in the buildup to a goal at Arsenal. On the same day, the lines had been placed on the wrong Crystal Palace defender, leading to a Brighton & Hove Albion goal being incorrectly disallowed.

And in October 2023, Liverpool had a goal ruled out for offside on the field at Tottenham Hotspur which the VAR mistakenly failed to correct. However, the error on the Luis Díaz goal was primarily around communication rather than the technology — an issue SAOT would not be able to fix by itself, but a less complicated process may help to prevent it happening again.

So what is semi-automated offside technology?

Developed by technology company Genius Sports, the Premier League says it creates a “more efficient placement of the virtual offside line” by taking the mapping of the relevant players out of the hands of the VAR and into the control of technology.

Rather than a referee placing lines onto a 2D TV screen, SAOT will plot the players in 3D.

It will also bring an “enhanced in-stadium and broadcast experience for supporters.”

What does it look like?

This is as important as any part of this project. It was incredibly difficult to visualise offside decisions, and now a 3D animation will take fans will effectively in line with the assistant referee.

The animation, which is similar to that produced by goal-line technology, will be shown at the stadium, on TV and also posted on the @PLMatchCentre X account.

The body parts of the attacker which is deemed offside (or not, should he be onside) is highlighted, and a simulation will create a “wall” indicating the offside line. If a player is offside, the relevant part of the body will break through that “wall.”

Unlike SAOT in other competitions, the animation will not move directly in line with the two players as they can appear over the top of each other and cause confusion. However, it remains to be seen if fans are happy with this method.

It should be far easier to understand for supporters at the ground or watching on television, and fewer delays should lead to less criticism — in theory.

The animation in the Champions League tends to take several minutes to be shown, as it’s overlayed onto the original TV coverage. In the Premier League and the FA Cup, it will be standalone so should be much quicker.

What was the first goal to be disallowed through SOAT?

Fabian Schär’s late “winner” for Newcastle United against Brighton & Hove Albion in the FA Cup was chalked off through SOAT on March 2. Brighton went on to win the game in extra time.

By the tightest of margins 😲

Fabian Schär with a well-taken finish, but the semi-automated offside technology steps in to disallow the goal!#EmiratesFACup pic.twitter.com/0CuCoJGnX0

— Emirates FA Cup (@EmiratesFACup) March 2, 2025

What was the first Premier League use of SOAT? And its first disallowed goal?

In Manchester City’s thriller with Crystal Palace on April 12, the referee’s call of no goal was checked and confirmed by the VAR — with Palace forward Eberechi Eze deemed to be in an offside position.

#MCICRY – 28′

The referee’s call of no goal was checked and confirmed by the VAR – with Eze in an offside position. pic.twitter.com/uCxUyVJbNi

— Premier League Match Centre (@PLMatchCentre) April 12, 2025

Arsenal fans will be delighted to know that Kieran Tierney’s opener against Brentford was the first goal to be ruled out via SOAT, after he was deemed to be offside before heading home on April 12.

#ARSBRE – 26′ VAR OVERTURN

VAR checked the referee’s call of goal – and established that Tierney was in an offside position and recommended that the goal was disallowed. pic.twitter.com/9jBazPN6mu

— Premier League Match Centre (@PLMatchCentre) April 12, 2025

Why is SAOT better?

Accusations of human error — sometimes founded, others more conspiracy theory — have often dogged VAR and offside. By taking the process out of the hands of the VAR and into the control of software, talk of operator bias should be put to bed.

It’s semi-automated because the VAR still has to confirm the result, and the technology cannot tell whether an attacker is actively involved in play or confirm the ball was touched by a teammate of that player.

The VAR also has to validate the kick point, because there is no chip in the ball in the Premier League version of the technology.

SAOT automates the mapping process and produces a result much more quickly. It removes all subjectivity from this part of the process, and the average time taken for an offside VAR review has been cut by an average of 30 seconds. But it will often save a lot more time. In a game between Chelsea and Tottenham Hotspur at the start of April, an offside review with a cluster of bodies took over four minutes. In offline trials of SAOT, it was two minutes quicker.

Time taken definitely erodes confidence. So, if SAOT can make everything noticeably quicker we might at least lose one of VAR’s areas of criticism.

The Premier League also believes that SAOT increases confidence in decision-making by reducing the reliance on manually checking all potential offsides — therefore reducing the likelihood that a potential decision is missed by VAR, like the one in Arsenal vs. Brentford.

How does SAOT work?

Incredibly, the Premier League’s SAOT uses a FIFA-validated iPhone-based system known internally at Genius Sports as “Dragon,” rather than lower frame rate broadcast cameras. There are 30 iPhones (the number may vary slightly by stadium design), model 14 or newer, installed under the roof of the 20 Premier League grounds.

These cameras provide optimal tracking for the ball and all 22 players, recording 10,000 surface “mesh” data points per player on all limbs and extremities that are relevant for an offside decision — including the upper arm, toes, knees and head — so the system knows the exact position of a player at any given moment.

Data is captured at a rate of 100 frames per second — double the 50 frames per second used in the old offside technology.

All player and ball data is processed in real time, which triggers an alert to the VAR. In effect, an offside player can be automatically “flagged” in the SAOT software.

The VAR must then validate the kick point and the accuracy of the offside line, and that the offside player is the one who touched the ball or who impacted play, and then inform the referee who can confirm or change the on-field decision.

The referee will still have to go to the pitchside monitor if there is a subjective offside decision (for instance an attacker in the goalkeeper’s line of sight) to be changed.

Where might it fall short?

The game between AFC Bournemouth and Wolverhampton Wanderers in the FA Cup on March 1 featured an incredible eight-minute VAR check, featuring two possible handballs and an offside.

The goal was eventually ruled out for offside, but the VAR was unable to use SAOT and had to revert to the old “crosshairs” technology.

Ahead of its introduction, the Football Association had made it clear that “the VAR will still have the option to draw crosshairs as a backup to the SAOT system if required. This process may be necessary in ‘edge cases’ where several players block the view of the ball or other players for the system’s cameras. This may occasionally result in the length of check we have seen previously in specific scenarios with VAR checking close offsides.”

Why isn’t there a chip in the ball, and does it matter?

The chip in the ball undeniable provides greater accuracy of the key touch. But Adidas, the provider for FIFA and UEFA, developed the original SAOT and it owns the patent for how the chip sits in the centre of the ball to ensure reliability of performance.

That patent means any other ball manufacturer would need to find a new way of balancing a chip without infringing the Adidas patent. As no top European league has a contract with Adidas, they’ve had to develop their own software.

But the chip system is so much more expensive that it’s only used in major tournaments like Euro 2024 and the World Cup. Even for the Champions League, UEFA uses a non-chip system like in the Premier League.

Without the chip, it has to work slightly differently. SAOT will suggest a kick point to the VAR and automatically create the offside line to that frame. The VAR then checks it’s the correct frame before approving the final decision.

Tony Scholes, the Premier League’s chief football officer, said earlier this season that he doesn’t believe the lack of a chip will be a problem.

“We believe we’re going to be adopting the best system and the most accurate system without the need for the chip in the ball,” he insisted. “We believe it to be the most accurate and the most futureproof system as well and that’s why we went with that.”

Between the frames, optical tracking is able to interpolate the player and ball movements with the system providing a continuous flow of data.

Right now we only have the official line to go on, the proof will come when we see it in action — the Premier League has certainly done plenty of testing.

So why does the Premier League think its system is more accurate?

This comes down to the method of mapping players and the number of cameras used.

The system used by FIFA and UEFA maps only 29 data points on the players — yet with the Premier League it’s 10,000 surface “mesh” data points.

FIFA and UEFA have 10-12 cameras in the stadium roof, in the Premier League it’s, on average, 30.

Broadcast cameras are used by FIFA and UEFA, at 50 frames per second. In the Premier League, the iPhones are twice the speed at 100 frames per second.

So the Premier League’s SAOT is supposed to be far more precise — let’s wait and see.

More accurate? So more offside goals, and “toenail” decisions?

This is good news, because the Premier League is going to retain the existing “tolerance level,” sometimes referred to as “thicker lines,” which gives a “benefit of the doubt” to the attacker of around 5cm.

It was introduced in 2021-22 after complaints about those so-called “toenail” calls where you can barely tell that a player is offside.

No other league with SAOT is using a tolerance level, instead making the most marginal of calls — as seen in the image below from the World Cup.

If the Premier League had removed the “tolerance level” we’d definitely have seen more goals disallowed, as there are many across a season which fall into this category.

However, if English football is keeping it, that might suggest that the Premier League isn’t yet totally happy with its accuracy. The whole point of the “tolerance level” in the “crosshairs” technology was to compensate for the inaccuracies and inconsistencies.

So, in English football, we won’t be going back to the incredibly tight offside calls we saw when VAR was first introduced. However, there will always be the marginal point when onside becomes offside — you cannot change that whatever system you have.

Will there still be any long delays for VAR checks?

Longer delays should be rarer, because SAOT means the VAR won’t have to go through the manual process of mapping the players.

However, there will be occasions when there are subjective elements to a decision. Is a player interfering with play? Has there been a “deliberate play” of the ball by the defender? Is an attacker in the line of vision of the goalkeeper? Those decisions, and others with multiple offside elements, will take longer.

There will also be situations where players block each other in the system’s cameras, or there may be multiple checks in one phase — like in the Bournemouth-Wolves FA Cup tie.

For instance, there was an offside check in Everton vs. Manchester United earlier this season which took over three minutes, and SAOT would not have improved that as it wasn’t purely related to player positions.

In the Champions League too, there can still be lengthy delays.

Will SAOT be used for all offside decisions?

No, so it’s still possible for a corner to result from a missed offside.

The VAR will only activate SAOT in one of the match-changing moments covered by VAR — goals, penalties and red cards.

What about the delayed offside flag?

While it’s true SAOT can work out player positions quickly, as its only for use on VAR reviews we haven’t seen the end of the delayed offside flag.

Play will still continue in an attacking situation until the end of the phase, when the assistant will raise their flag.

Is SAOT in any other leagues?

Serie A was the first European domestic league to switch to SAOT, introducing it in January 2023 after a high-profile VAR error early in that campaign had seen a stoppage-time winning goal for Juventus incorrectly disallowed. Mexico’s Liga BBVA MX also introduced it in January 2023, and it has been used in the CONMEBOL Libertadores, South America’s equivalent of the Champions League.

LaLiga brought in SAOT at the start of the 2024-25 season.