Windows 11 update schedule explained: A, B, C, and D releases

Microsoft follows an A, B, C, and D monthly servicing cadence for Windows 11 rather than releasing updates randomly.
The B release (Patch Tuesday) delivers mandatory security and quality updates, while the D release previews next month’s non-security fixes and features.
Week C is primarily used for Release Preview Insider builds before changes reach the public through the D release.
Understanding the update pipeline helps users know when to expect new features and decide whether to install optional preview updates.

Microsoft doesn’t release Windows 11 updates at random. Instead, the company follows a structured monthly release cadence known internally as the A, B, C, and D release schedule. Each letter represents a different week of the month and determines the type of cumulative update users can expect.

Understanding this schedule can help you decide when to install updates, know why some updates are mandatory while others are optional, and understand when new features and bug fixes are likely to arrive.

In this guide, I’ll explain what each release means and how Microsoft’s monthly update cycle works for Windows 11.

What is the A, B, C, and D release cadence?
What is an Out-of-Band (OOB) update?
Which Windows 11 updates should you install?
Windows 11 update release schedule at a glance
How updates move from preview to Patch Tuesday
Pureinfotech’s Take

What is the A, B, C, and D release cadence?

The A, B, C, and D naming convention refers to the week of the month when Microsoft typically releases cumulative updates for Windows 11.

The cadence allows the company to release security fixes on a predictable schedule while also testing quality improvements before they become mandatory updates.

Although the company doesn’t publicly advertise these letter designations to consumers, they’re widely used in Microsoft’s documentation and by IT administrators to describe the monthly servicing cycle.

Here’s a quick overview:

Release	Week	Purpose
A	First week	No scheduled cumulative updates
B	Second Tuesday	Mandatory security and quality update (Patch Tuesday)
C	Third week	Usually no scheduled releases for Windows 11
D	Fourth Tuesday	Optional non-security preview update

Week A release

The first week of the month is generally a quiet period.

Microsoft doesn’t normally publish scheduled cumulative updates during this week. Instead, engineers monitor the health of the previous month’s releases, analyze telemetry, investigate reported issues, and prepare upcoming updates.

This buffer period gives the company time to identify unexpected problems before the next Patch Tuesday rollout.

While no updates are typically planned for Week A, Microsoft can still release an emergency update if a serious issue requires immediate attention.

Week B release (Patch Tuesday)

The B release is Microsoft’s most important monthly update.

Released on the second Tuesday of each month, this cumulative update contains:

Security patches.
Bug fixes.
Reliability improvements.
Previously tested non-security fixes.

Because it includes security updates, Windows 11 automatically downloads and installs the B release on most consumer devices.

These updates are cumulative, meaning they include all previously released fixes. If you skipped an earlier update, installing the latest B release brings your device fully up to date.

For most users, this is the update that matters the most. Keeping your computer current with the monthly Patch Tuesday release helps protect it against newly discovered security vulnerabilities while improving overall stability.

Week C release

The C release is no longer a regular cumulative update for Windows 11. In the past, Microsoft used the third week of the month to release optional non-security preview updates for supported versions of the operating system. Today, this week generally serves as a transition period before the optional preview update is released during Week D.

Although Windows 11 consumer devices typically don’t receive a scheduled cumulative update during Week C, Microsoft frequently uses this period to publish Release Preview channel builds for Insiders. These builds are among the final stages of testing before fixes, features, and other changes are released to the public through the optional D release.

Release Preview builds allow Microsoft to collect feedback and telemetry from Insider devices before the same non-security improvements become available to all users as an optional preview update.

After additional validation, those fixes are then included in the following month’s mandatory B release (Patch Tuesday).

Week D release (Optional preview update)

The D release arrives during the fourth week of the month and serves as a preview of next month’s Patch Tuesday update.

Unlike the B release, this update doesn’t include security fixes. Instead, it focuses on:

Fixing bugs.
Improving reliability.
Enhancing performance.
Introducing new Windows features that have completed testing.

The purpose of the D release is to validate these improvements before Microsoft includes them in the following month’s mandatory security update. These updates are optional.

Windows won’t install them automatically on most consumer devices. Instead, you must manually open Settings > Windows Update and click “Check for updates.” Users who manually request available updates are commonly referred to as seekers.

Network administrators may also deploy these preview updates to a small group of devices to verify application compatibility and ensure there are no unexpected issues before the fixes are released to all users.

If you don’t install the optional preview update, you’ll typically receive the same non-security fixes automatically as part of the next month’s Patch Tuesday (B) release.

What is an Out-of-Band (OOB) update?

Not every Windows update follows the A, B, C, and D schedule.

When the company discovers a critical security vulnerability or a severe operating system issue that can’t wait until the next Patch Tuesday, the company may publish an Out-of-Band (OOB) update.

These emergency releases can occur at any time during the month and are intended to quickly resolve issues affecting a large number of devices.

Depending on the severity of the problem, the company may recommend installing the update immediately or automatically deliver it through Windows Update.

Which Windows 11 updates should you install?

For most users, installing the monthly B release is all that’s necessary. These updates contain the latest security fixes and all previously tested quality improvements, including new features.

The D release is primarily intended for users who want early access to non-security bug fixes or new features, as well as organizations that want to validate upcoming changes before the mandatory rollout.

If your computer is working properly, there’s usually no need to install the optional preview update unless it contains a fix for a problem you’re experiencing.

Out-of-Band updates should generally be installed if they address an issue that affects your device, particularly if Microsoft identifies the problem as security-related.

Windows 11 update release schedule at a glance

This table will explain the release schedule of each update and its purpose.

Release	Timing	Security updates	Automatic installation	Primary purpose
A	First week	No	No	Monitoring and preparation
B	Second Tuesday	Yes	Yes	Monthly security and quality update
C	Third week	Rare	No	Buffer period or targeted servicing
D	Fourth Tuesday	No	No	Optional preview of next month's fixes
OOB	Any time	Usually	Depends	Emergency fixes for critical issues

How updates move from preview to Patch Tuesday

If you’ve ever come across one of my articles previewing an upcoming Patch Tuesday update, you may have noticed that I often publish the story before Microsoft officially releases the mandatory update. That’s because I follow the company’s monthly servicing cadence.

I typically begin by covering the non-security fixes, new features, and changes that first appear in the Release Preview channel and later become available to the public through the optional D release. As Microsoft continues moving the update through its release pipeline, I update the article with additional improvements, security fixes, and any last-minute changes until the final B release (Patch Tuesday) is available to everyone.

It’s also worth noting that Microsoft names cumulative updates after the month in which they are first released, not the month in which they become mandatory for most users. For example, an optional preview update released in July is considered the July 2026 update, even though its non-security fixes and new features won’t reach all Windows 11 devices until the mandatory August Patch Tuesday update.

Pureinfotech’s Take

One thing I’ve learned from covering Windows for years is that Microsoft’s update schedule is far more predictable than many people realize. Once you understand how the A, B, C, and D cadence works, it becomes much easier to know when new features are actually coming and whether an update is worth installing right away.

Personally, I stick with the monthly B release on my primary computer unless a D release includes a fix I specifically need. Preview updates have become more reliable over the years, but they’re still part of Microsoft’s final validation process, and I’d rather let that process play out before installing them on a computer I depend on every day.

I also think understanding this release pipeline helps explain why my Patch Tuesday coverage often starts weeks before the mandatory update arrives. Those changes don’t suddenly appear on release day. They move through several stages of testing before reaching every Windows 11 device.

What are your thoughts about Microsoft’s monthly Windows update schedule? Do you usually install optional preview updates or wait for Patch Tuesday? Let me know in the comments.