5.5 million people watched Valve’s Dota 2 documentary over the weekend

Valve’s Dota 2 is one of the biggest online PC games partially because it is free. Now, Valve’s Dota 2 movie Free to Play is one of the most-watched documentaries ever for the same reason.

Last Wednesday, Valve released Free to Play: The Movie on Steam and YouTube. Since then, more than 5.5 million people have watched the documentary about the company’s popular multiplayer online battle-arena title. Valve claims this makes it one of the most-watched documentaries ever over an opening weekend — although it obviously has an advantage over movies like Michael Moore‘s Fahrenheit 9/11, which was only available in theaters and charged for admittance. Valve isn’t charging for its film, and it isn’t even running ads on the YouTube video. That makes Free to Play more a piece of marketing for Dota 2 while Fahrenheit 9/11, the top-grossing documentary ever, earned nearly $24 million in its opening weekend.

Free to Play follows several professional Dota 2 players as they struggle to maintain a balance in their personal lives while simultaneously striving to dominate the competitive-gaming scene. You can watch the full film below:

Free to Play isn’t the first gaming-focused documentary. In 2007, studio Picturehouse released The King of Kong: A Fistful of Quarters, which tracked a competition between the two top Donkey Kong players in the world at that time. That film earned $51,493 in its first weekend.

Dota 2 is one of the biggest titles in e-sports, which serves as the central goal for most of the subjects in Free to Play. Each year, Valve holds a world-championship competition called The International, which has teams facing off against each other for million-dollar prize pools.

The multiplayer online battler has hundreds of thousands of daily active players who are all spending money on in-game cosmetic items and different characters. In 2013, gamers spent around $80 million on Dota 2, and that’s likely going to grow significantly throughout this year.

Part of that growth will come from new players who are attracted to the game by watching the online competitions, which always draw hundreds of thousands of viewers. Another part of that growth might come from marketing like Free to Play, which serves as a feature-length advertisement for Dota 2.