Unity Technologies has announced a milestone: the company said that its installed base of developers has passed the 500,000 mark, doubling in just over six months, while the number of users who have installed the plug-in that enable Unity games to run on a Web browser has passed 60 million.

[ad#Google Adsense 300×250 in story]Unity was originally developed as a game engine for the Mac but has grown well beyond that over the years, becoming a vehicle for browser-based game development, games on iOS, game consoles and more. The developer says that Unity is now the most widely used middleware on the iOS platform, with more than 1,500 apps in the App Store using it. Unity for Android made its debut in March.

Browser-based games that use the Unity engine include EA’s Tiger Woods PGA Tour Online and Bigpoint’s Battlestar Galactica Online. Unity-based Web games are playable in Mac and PC browsers using a plug-in that customers can install themselves.

Unity Technologies is holding its fifth annual developer conference, Unite 11, in San Francisco this September. More details are available online.