The popularity of watching eSports continues to soar worldwide, with 2.4 billion hours of eSports video viewed during 2013, according to a newly released IHS Technology report.

According to the report (via Gamasutra), that figure is up from 1.3 billion hours in 2012 and is only expected to continue growing: By 2018, that number will reach an estimated 6.6 billion hours. 2013 marked the first time that eSports viewing online surpassed that of television, and it did so by a large margin–almost three times as many hours were spent watching eSports online than on television. By 2018, online viewing will represent 90 percent of time spent watching eSports.

As you’d expect, given its massive player base, League of Legends was the most popular game among eSports viewers, followed by Dota 2 and StarCraft II.

“ESports videos have rapidly transformed from a niche activity into a widely-watched, global, cross-platform entertainment category,” said IHS digital media research director Dan Cryan. “Several factors are contributing to the surge in esports viewing. These include the fact that key game titles have reached maturity and game publishers are taking a major role in promoting esports competitions. Furthermore, eSports viewing has been boosted by the emergence of online video platforms that are capable of handling large-scale live audiences.”

The eSports video market will be worth $300 million annually by 2018, IHS said, which goes a long way in explaining why YouTube recently made the move to acquire game streaming service Twitch, though the deal is not yet complete.

“While advertising in and around games has often proved to be a difficult proposition, advertising in online video is commonplace,” said IHS games research director Piers Harding-Rolls. “This form of advertising gives games companies a much better opportunity of accessing the advertising value chain in a successful and meaningful way and offers these companies a route to profitable return on investment from their eSport initiatives.”

This is far from the first indication we’ve had that watching eSports–whether it’s a “legitimate” sport or not–is becoming increasingly popular. Last year, more than 32 million people watched the League of Legends Season 3 World Championships (pictured above), and there were over 1 million concurrent viewers of the recent ESL tournament. Developers and publishers have more frequently made supporting eSports a priority, including EA and Activision, and both the Xbox One and PlayStation 4 allow gamers to stream their live gameplay online through Twitch, all of which should only help eSports viewing to continue to grow.

Have you spent any time watching eSports online in the past year and, if so, which games did you watch?