The bout is a much-awaited rematch following a controversial decision in the first match.
It was given as a draw, along with one bizarre 118-110 scorecard in favour of Canelo, despite it looking like Golovkin had edged it.
The fight is on BT Sport and is priced at £16.95 in the UK – a price which has riled fans.
And a warning has been issued about streaming the fight online.
Huge fines have been slapped on those who flaunt laws – in some cases up to £85,000.
“It is getting harder and harder to watch live sport illegally”
“Consumers need to be aware that streaming without the right permissions or subscriptions is no longer a grey area,” explained The Federation Against Copyright Theft (FACT).
“In April last year the EU Court of Justice ruled that not only was selling devices allowing access to copyrighted content illegal but using one to stream TV, sports or films without an official subscription is also breaking the law.
“The public should be aware that misusing their TV subscriptions has serious repercussions. For example, customers found to be illegally sharing paid-for content can have their subscription account terminated immediately and can expect to be prosecuted and fined.”
Kieron Sharp, CEO of FACT, said any way of avoiding the official provider to access the fight is illegal.
He said: “FACT is leading the way in combatting digital piracy and working with PIPCU and industry to crackdown on illegal streaming and to hold those behind them accountable for their actions.
“It is getting harder and harder to watch live sport illegally and so boxing fans should be aware that if they were planning to watch the fight this way they are breaking the law.”
Detective Inspector Nick Court of the City of London Police’s Intellectual Property Crime Unit also added: “By using illegal streaming sites you can open yourself up to several risks; some set-top boxes do not go through rigorous electrical testing and are therefore at risk of catching fire or giving electric shocks.
“By using legitimate providers these risks can easily be avoided. Watch it live, watch it legally.”
The fight is live on BT Sport around 4am today.