These were the 12 highest-grossing games of 2018 on Steam, the biggest platform in PC gaming

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Steam is a digital marketplace and video game platform used by tens of millions of PC gamers on a daily basis. The most popular games on Steam have more than 500,000 players online at any given time.
Valve, the company behind Steam, recently released a list of the 100 highest-grossing games of 2018. The top-earning games are on sale until January 3rd, 2019.
There are almost 20,000 games for sale in the Steam marketplace, but some of the highest-earning titles are actually available for free, including 3 of the top 12.

With the close of 2018, video game retailers are offering a variety of capstone sales to celebrate the best games of the year. Steam, the largest digital marketplace for PC games, is no different, offering discounts of up to 80% on the top games of 2018 during the Steam Winter Sale.

Alongside the winter sale, Steam has released a list of the 100 top-selling games of 2018, based on gross revenue. That includes all sales of digital content, beyond the price of the base game. Steam separated the games into four tiers based on their earnings: platinum, gold, silver, and bronze.

Below, we've taken a look at all 12 games in the platinum rank. Surprisingly, only three of the platinum games were released during 2018, and another three are actually free-to-play. Because the games are judged by gross revenue, free-to-play games are boosted by smaller, microtransactions that charge players for in-game currency and other incremental content. Older titles can also continue bringing in revenue by selling new expansion content.

Keep in mind that not all PC games are available on Steam, so popular titles like "Fortnite," "Overwatch," "League of Legends," and "World of Warcraft" are not considered.

Here are the 12 highest-grossing games of 2018:

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"Warframe" by Digital Extremes

"Warframe" is a free-to-play online action game with a mix of mission-based objectives and open world gameplay. "Warframe" has been around since 2012, but the game has been experiencing a massive surge in popularity, thanks to ongoing support from developer Digital Extremes.

While the game is free, "Warframe" offers a wide selection of armor, weapons, and items that can bought up front with real-life cash. Dedicated players can buy the same items with currency they earn while playing the game.

"DOTA 2" by Valve

"DOTA 2" is a free-to-play game developed by Valve, the same company that owns and operates Steam. Originally a mod of "Warcraft III," "DOTA 2" has been around for more than a decade and helped create a brand-new genre of video game, the Multiplayer Online Battle Arena, or MOBA.

DOTA 2 features more than 100 playable characters and primarily earns revenue by selling cosmetic items for use in-game. This year, Valve also introduced Dota Plus, a monthly subscription that charges users for access to advanced statistics and exclusive features.

"Tom Clancy's Rainbow Six Siege" by Ubisoft Montreal

"Rainbow Six Siege" has been a shocking success in the very competitive market for PC first-person shooters. The "Rainbow Six" series of squad-based shooters dates back to the 90s, but "Siege" has shifted the franchise formula.

Players now choose from an ever-increasing roster of soldiers with special abilities called "operators." Ubisoft has been able to keep its player base invested in the game by releasing new operators regularly, and the cost of new operator packs helps the game stay sustainable as it enters its fourth year.

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