Windows 8
Several versions of Windows 8 were made available to software developers well before the final release. The first of these, the Developer Preview, came out in September 2011. On February 29, 2012, Microsoft released a beta version of Windows 8.0 known as the Consumer Preview. Anyone could register online to download this version for free. After the Consumer Preview, a final preview named "Release Preview" was released on May 31, 2012.