The Update BureauBesides the monthly security update, Microsoft releases an optional preview update later in the month, usually in the fourth week.
What's in it
The preview contains the fixes and new features planned for the next month's security update, but no new security fixes. It lets people try the changes a few weeks early.
Should you install it?
You don't have to. The next monthly security update, on the second Tuesday of the following month, includes everything in the preview. Each preview page on this site tells you that date.
Install a preview only if it fixes a problem you actually have and you can't wait.
How it shows up
Windows does not install previews automatically: Windows Update lists them as optional with a Download and install link. On Windows 11, turning on Get the latest updates as soon as they're available in Settings › Windows Update makes Windows install them, and turns on some new features earlier.
Previews and Windows Insider builds are different
Windows Insider builds are test versions for volunteers and can change a lot. Optional previews are finished updates for everyone, just released early.
Edited by the site editor. Written with AI from Microsoft's own documents, checked by rules and a second AI. How we work · Report a mistake