SAN FRANCISCO — Microsoft is giving people a peek into Windows 8.1, a free update that promises to address some of the gripes people have with the latest version of the company’s flagship operating system.

Although the preview version of Windows 8.1 is meant for Microsoft’s partners and other technology developers, anyone will be able to download it for free starting Wednesday, exactly eight months since desktops, laptops and tablets with Windows 8 went on sale. The version of the Windows 8.1 update meant for the general public will come out later in the year, though a specific date hasn’t been announced.

Many of the new features have been shown off already. A three-day Build conference, which starts Wednesday in San Francisco, will give Microsoft developers a chance to learn more about the new system and try it out. It also will give the company a chance to explain some of the reasoning behind the update and sell developers on Microsoft’s ambitions to regain relevance lost to Apple’s iPad and various devices running Google’s Android software.

There’s also speculation that Microsoft could show off a new, smaller version of its Surface tablet computers. One of the new features is the ability to work well on smaller-screen devices.