Steam has confirmed it will bring its digital distribution service Steam to Mac this April.
The service will launch with a variety of games from Valve's library, including Left 4 Dead 2, Team Fortress 2, Counter-Strike, Portal and the Half-Life series.
The newly-announced Portal 2 will be Valve's first simulaneous Mac and Windows release when it arrives this Christmas.
The launch of the Mac edition will introduce a new feature called Steam Play, which works in conjunction with Steam Cloud to allow consumers to play their purchased games on both PC and Mac free of charge.
"As we transition from entertainment as a product to entertainment as a service, customers and developers need open, high-quality Internet clients," said Valve president Gabe Newell.
"The Mac is a great platform for entertainment services." Director of business development Jason Holtman added: "Our Steam partners, who are delivering over a thousand games to 25 million Steam clients, are very excited about adding support for the Mac."
Valve has previously teased this announcement with a series of teaser images parodying familiar Apple ad campaigns.
"We looked at a variety of methods to get our games onto the Mac and in the end decided to go with native versions rather than emulation," said John Cook, Director of Steam Development.
"The inclusion of WebKit into Steam, and of OpenGL into Source gives us a lot of flexibility in how we move these technologies forward. We are treating the Mac as a tier-1 platform so all of our future games will release simultaneously on Windows, Mac, and the Xbox 360. Updates for the Mac will be available simultaneously with the Windows updates. Furthermore, Mac and Windows players will be part of the same multiplayer universe, sharing servers, lobbies, and so forth. We fully support a heterogeneous mix of servers and clients. The first Mac Steam client will be the new generation currently in beta testing on Windows."
Meanwhile Valve's proprietary engine Source is also being made available for Mac - with Portal 2 benefitting from the dual target platform approach.
"Checking in code produces a PC build and Mac build at the same time, automatically, so the two platforms are perfectly in lock-step," said Josh Weier, Portal 2 Project Lead. "We're always playing a native version on the Mac right alongside the PC. This makes it very easy for us and for anyone using Source to do game development for the Mac."
Support for the Mac in Source and Steamworks is available to third parties immediately. Valve says developers should contact Jason Holtman at email@example.com.