Windows 10's new light desktop background logo.

Microsoft’s “Patch Tuesday” occurs on the second Tuesday of each month. This is the day when, like clockwork, Microsoft releases large update packages for Windows 10, Windows 7, Microsoft Office, and its other software.

What Is Microsoft’s Patch Tuesday?

Sometimes called “Update Tuesday,” Patch Tuesday is an unofficial term for the day when Microsoft releases update packages for the Windows operating system and other Microsoft software applications, including Microsoft Office.

As Microsoft patches security vulnerabilities, it doesn’t release those patches immediately. Instead, the company gathers those fixes into a larger update, which is released on Patch Tuesday.

Microsoft does this to make the update process as predictable as possible for administrators. IT professionals know that patches will arrive on the second Tuesday of each month, and they can make plans to test or install them. It should be easier than continually applying smaller patches and more predictable than huge patches arriving on a random day of the month.

When Is Patch Tuesday?

Patch Tuesday occurs on the second Tuesday of each month. More precisely, it occurs on the second Tuesday of each month in North America.

Microsoft doesn’t have a guaranteed time these patches and Microsoft’s information bulletins about them will be released. These updates generally arrive around 10 a.m. Pacific Standard Time, but they may be released later in the day.

Windows 10 checks for updates about once per day. The average Windows PC should automatically download these updates via Windows Update by Wednesday afternoon if it’s powered on and connected to the internet. Of course, administrators may choose to delay and test these updates before deploying them to PCs in their organizations.

Updates Aren’t Only Released on Tuesdays

As you might have noticed, Patch Tuesday isn’t the only date updates arrive. In some cases, Microsoft will issue “out-of-band” updates for particularly critical security flaws, especially ones that are being exploited in the wild.

However, if a security hole isn’t being exploited in the wild and it’s okay to wait a few weeks, Microsoft will wait for Patch Tuesday to issue that update.

Even if you do get one or more smaller patches in a month, there’s always bigger update coming on Patch Tuesday. It contains all the updates that didn’t have to be rushed out.

Patch Tuesday Is For “B” Updates

Windows Update showing an optional update.

In Microsoft’s update parlance, Patch Tuesday updates are called “B” updates because they’re released in the second week of each month.

Microsoft also issues optional update packages in the third or fourth weeks of the month. They’re known as the “C” and “D” updates. These include bug fixes and improvements for problems that aren’t security holes. After these updates are tested, their fixes make it into next month’s B update on Patch Tuesday.

These C and D updates now appear as “optional updates” in Windows Update on Windows 10.

Patch Tuesday Isn’t Just For Microsoft

Other companies have chosen to join Patch Tuesday to make things easier for system administrators to update their systems with security patches.

For example, Adobe also releases security updates for its software like the Adobe Flash Player browser plug-in and Acrobat Reader PDF viewer on Microsoft’s Patch Tuesday.

Patch Tuesday Isn’t For Windows 10’s Big Updates

Microsoft now releases big updates to Windows 10 once every six months. For example, Windows 10’s last big update was the May 2019 Update, and it was preceded by the October 2018 Update.

These updates aren’t released on Patch Tuesday. They’re released on whatever day Microsoft decides to release them.

Even after the official release of each major update, the rollout process is slow. Big updates like these may not be automatically installed on your PC until months later, as Microsoft now uses AI to determine when it’s confident the update is safe to install for your combination of hardware and software. You can still choose to skip the wait and install them immediately, but Microsoft says you have better odds of a good experience if you decide to wait.

That’s very unlike Patch Tuesday updates, which don’t contain new features. They contain important security updates and already-tested bug fixes. By default, they’re automatically installed for all Windows users as soon as possible.

You can view information about Windows 10 updates on Microsoft’s Windows 10 Update History page.

Profile Photo for Chris Hoffman Chris Hoffman
Chris Hoffman is Editor-in-Chief of How-To Geek. He's written about technology for over a decade and was a PCWorld columnist for two years. Chris has written for The New York Times and Reader's Digest, been interviewed as a technology expert on TV stations like Miami's NBC 6, and had his work covered by news outlets like the BBC. Since 2011, Chris has written over 2,000 articles that have been read more than one billion times---and that's just here at How-To Geek.
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