Fed Square hosted large crowds despite a 2am AEDT kick-off, fans were not deterred by the prospect of a long, sleepless night.

"Thank god for Leckie, his back must be sore carrying the whole team," said Socceroos fan Michael Brazier.

A goal from Socceroos Matthew Leckie was enough to secure Australia's 1-0 victory over the Danish team, launching Australia into their first knockout-stage in 16 years.

Fans predicted the outcome of the match correctly, holding signs reading 'Big 2006 energy.'

"My expectations were low so it was all the sweeter," said fan Julian Bedford.

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Socceroos fan correctly chanted "You're red, you're white, you're going home tonight" to the Danish crowd as the sky turned red with flares.

Fed Square, in Melbourne's centre, is the favoured place to watch Socceroos matches after footage from Australia's win against Peru in the qualifying rounds went viral.

Since Germany 2006, the Socceroos' first World Cup appearance in 32 years, nail-biting all-nighters cheering on the green and gold have been a rite of passage for fans like Tom Zwar.

"That was probably the first time my parents let me stay up past midnight, especially on a school night it was unheard of," Mr Zwar, now 26, told AAP.

"But it's just something you have to do, even if you're a bit groggy the next day, you just have to cop it because it's the World Cup.

"It just means so much and it only comes around once every four years."

As the game drew to a close, they lit flares and danced and chanted to celebrate the win.

The scenes of wild jubilation have since gone viral.

- with Australian Associated Press