Valve Software on Thursday revealed that its popular online shooter Team Fortress 2 is adopting the "free-to-play" business model on PC, and will be supported solely by virtual item sales.

It's the first time that Valve has applied the business model to one of its own internally-developed games. Team Fortress 2 launched on PCs and consoles in 2007 as part of The Orange Box compilation.

Players who bought Team Fortress 2 (digitally or at retail) prior to the "Uber Update," released today, will have a "premium account."

These accounts will give players access to "a few extra features, including access to rare and cosmetic items through random item drops, the ability to store more items in your backpack, and more powerful trading and crafting abilities," according to Valve.

Outside of those extra features, the gameplay experience will be "identical," the studio said. Valve added, "The entire game can be played without making a purchase. All game modes, classes, and maps are available. Nearly every weapon is available through achievements, drops, or crafting."

Gamers who purchase any item from Team Fortress 2's digital storefront the "Mann Co. Store" will also be granted premium account privileges.

Valve introduced the Mann Co. Store in September last year, sparking speculation that the aging Team Fortress 2 could be going fully free-to-play. Users can spend real money to buy virtual items such as weapons for the various character classes, and a wide variety of hats.

Those who bought Team Fortress 2 before it went free will also receive a "Proof of Purchase hat" for any character. More details on the update can be seen at the official free-to-play FAQ.

The move closely follows Valve's recent introduction of third-party games on Steam that implement the free-to-play model.