What is 'Snicko' and how does it work at the World Cup?

Sweden's fourth goal against Tunisia at the World Cup on Sunday night was controversially awarded following the use of Snickometer technology.

Mattias Svanberg scored just 18 seconds after coming on as a substitute in the second half by converting a Yasin Ayari free-kick during the 5-1 win.

Initially, Svanberg had been declared offside at the time the free-kick was delivered.

Following protests from Sweden's coaching staff and players and after a check by the Video Assistant Referee (VAR) team, the goal was later given.

Waveform technology that mirrors cricket's Snickometer (more commonly known as Snicko) judged that after the free-kick was taken, Sweden and Liverpool striker Alexander Isak got the faintest of touches on the ball - and when he did, Svanberg had moved back into an onside position, meaning the goal was allowed.

"It is a good finish by Svanberg, but I can understand why the Tunisian players will be disappointed because when you look at it, it didn't look like there was a touch," former Republic of Ireland striker Clinton Morrison said during BBC Radio 5 Live's coverage of the game.

"It must have been the slightest touch off the outside of his right boot. Credit to VAR, credit to the referee. They got it spot on."

Contact formContact formHow does the technology work and has it been used before?'Snicko' in sport is more traditionally associated with cricket, but in recent years, football has adopted similar technology.

The Trionda match ball, made by Adidas for this year's World Cup, has a microchip in it that can detect when the ball has been touched.

It is part of Adidas' Connected Ball Technology, allowing precise data such as every individual touch of the ball with a boot or hand to be immediately sent to the Video Assistant Referee in real time.

Adidas say the technology "enables faster in-game officiating decisions and more insight into gameplay than ever before."

When Svanberg's goal was awarded, replays showed a flat-line sensor on the screen that had a spike as the ball passed Isak's outstretched foot, confirming that he got a touch on the ball that was not necessarily obvious to the naked eye.

Similar technology has also been used at the 2022 World Cup and 2024 European Championships.

At the Qatar World Cup, 'Snicko' was able to prove Bruno Fernandes scored Portugal's opening goal during a 2-0 win over Uruguay.

His cross towards Cristiano Ronaldo in the penalty area was enough to beat goalkeeper Sergio Rochet, which Ronaldo celebrated while claiming he had headed the delivery in, although the technology then showed he did not touch the ball.

And at Euro 2024, Belgium had a goal disallowed against Slovakia following another 'Snicko' review.

Romelu Lukau had initially been awarded an equaliser, but the review using the technology clearly showed teammate Lois Openda handle the ball in the build-up to the goal.

Cricket's Snickometer is a decision-making technology system used to determine whether a batter has hit the ball during a video review.

The technology shows replays in frame by frame pictures, with a waveform created to display if there has been contact between bat and ball.

It was invented by English computer scientist Allan Plaskett during the mid-1990s, but it is no longer used in Tests in England. However, it is still used in Australia and New Zealand.

'Snicko' caused controversy during the 2025-26 Ashes series, with Australian batter Alex Carey given not out in the third Test due to "human error" by its operators. Carey was 72 not out at the time and went on to make 106 in the first innings in Adelaide.

The use of 'Snicko' in cricket is reducing as more advanced technology becomes available. It operates at 340 frames per second, less than the likes of Adidas' Connected Ball technology and UltraEdge, with the latter being used in Test matches taking place in England.

This article is the latest from BBC Sport's Ask Me Anything team.