Clicks on YouTube music videos are counting towards the US singles chart for the first time.
Billboard has said that a "major shake-up" means that data from the website is now one of the factors used to decide who makes it to number one in the Hot 100.
This week's US chart shows what is now possible: Baauer's Harlem Shake track - a hit on YouTube with thousands of copycat videos - has ranked at number one.
Physical sales combined with radio airplay was the traditional measure of deciding the Billboard Hot 100, with digital downloads and music streaming services being included in recent years.
But the inclusion of clicks on YouTube means that a viral video can now hit the top spot, even if it is being outsold or outplayed on the radio.
The new rule counts all official videos on YouTube, including Vevo.
It also, potentially, gives previously unknown musicians the chance to hit the big time.
As Billboard says about Harlem Shake: "It's the first song to start at the summit by an artist essentially unknown prior to charting".
Baauer's track rocketed to the top of this week's chart thanks to the weight of 103 million weekly streams.
The revised formula also sees the likes of Rihanna benefiting from YouTube clicks - as well as her recent Grammys performance - with Stay climbing from 57 to number three.
The UK top 40 is based only on sales, most of them now paid-for digital downloads.
The Official Charts Company (OCC) last year launched a separate Streaming Chart based on sites such as Spotify and We7.
However OCC managing director, Martin Talbot, says that YouTube views won't be included in the main Top 40 any time soon.
"The UK’s Official Singles Chart has been a purely sales based chart ever since it launched in 1952," he told Sky News.
"With singles' sales currently at an all-time high following nine years of continued year-by-year growth, there are currently no plans to incorporate streaming information in the UK."