Microsoft is confirming today, after recent reports, that the company has completed Windows 8.1 and is releasing it to manufacturing (RTM). The finalization of the Windows 8 update means that hardware partners can now ready systems running Windows 8.1 and Windows RT 8.1 for release on October 18th. For existing Windows 8 users, the update will be made available broadly on October 18th — with most regions getting access to a digital upgrade copy on October 17th via the Windows Store.

MSDN and TechNet have to wait until October 18th

Many had hoped MSDN or TechNet customers would get access to Windows 8.1 shortly after RTM, but Microsoft says this is not the case. MSDN and TechNet subscribers will need to wait until the general availability date of October 18th. The software maker doesn't explain why, but it appears the company will be putting "the finishing touches on Windows 8.1" during the coming weeks "to ensure a quality experience at general availability on October 18th."

The Verge has learned that Microsoft plans to address additional bugs and features with quick fix patches in the coming weeks ahead of the release. Windows 8.1 also includes improvements aimed at software developers, who would typically need access to 8.1 RTM a lot sooner than release. A Microsoft spokesperson tells us the company is "working with a limited set of partners who are building apps that will showcase the new functionality of Windows 8.1; however, we have nothing more to share at this time."

Lots of minor changes make for a big upgrade

Windows 8.1 includes a variety of minor changes that add up to a fairly significant update, especially just a year after the original Windows 8 release. Microsoft has made a number of interface changes, including smaller and larger Live Tiles, support for desktop wallpapers behind the Start Screen, and new parallax wallpapers. The Start button also sees its return, and an option to boot to the desktop. Microsoft has also improved multitasking of apps, multi-monitor support, and access to a number of PC settings in the touch-based "Metro" environment. Bing search is also integrated, along with Mail and built-in app improvements. Windows 8.1 hopes to address first-time user complaints from October 18th onwards, with a number of pointers around the OS initially, and a separate Help + Tips application.