Microsoft’s recent November 2025 update has finally shut down the popular KMS38 activator, a tool widely used to run Windows and Office without purchasing a legitimate license. It has run for so long that everyone has always wondered why Microsoft hasn't shut it down. But today it has finally happened, users who relied on this method have suddenly lost activation. So what can you do about it?

Takeaways:

  1. Learn how to activate Windows and Office after Microsoft breaks the KMS38 workaround.
  2. Windows activation issues after the latest update. KM38 is no longer working.

Why Did Microsoft Block KMS38?

KMS38 was developed as an open-source tool allowing users to activate Windows and Office by exploiting a loophole in Microsoft’s licensing system. For years, it enabled users to install official updates and use software features without paying for a license. However, such unauthorised activation is against Microsoft’s licensing terms and exposes users to potential security and stability issues.

With the November 2025 Patch Tuesday update, Microsoft patched the vulnerabilities exploited by KMS38. As a result, systems activated with this method are now flagged as unlicensed. They won't instantly encounter issues, but after about 30 days, the notice to Activate Windows will return.

Symptoms of the Activation Issue

If your system was activated using KMS38, you might experience the following:

  • Activation warnings or notifications in Windows or Office.
  • Reduced functionality or access to updates.
  • Persistent messages prompting you to purchase a genuine license.

How to Fix Windows 11 Activation Problems

First, determine if your Windows or Office installation is activated:

  • On Windows 10 or 11, open Settings > Update & Security > Activation. You will see your activation status here.
  • In Office, open any Office application, go to File > Account, and check your license status.

If activation has failed, your system will indicate it here.

Purchase a Genuine License

To restore activation, you need a valid product key or subscription. Microsoft licenses are affordable and can be purchased through the official Microsoft Store or authorised resellers. For example:

  • Windows 11 licenses can often be found online for around $10 to $20. There are quite a lot of options over on Alibaba for around $2USD as well, which work fine. For the sake of 2 bucks, it's worth not worrying about pirating anything.

Purchasing legitimate licenses ensures that your software remains secure, receives updates, and complies with legal requirements.

Activate Windows and Office

Once you have a valid license, activate your software as follows:

  • For Windows, open Settings > Activation, select Change product key, enter your purchased key, and follow the prompts.
  • For Office, open any Office app, sign in with your Microsoft account linked to your subscription or enter your product key under File > Account > Change License.

Link Your License to a Microsoft Account

Linking your Windows license to your Microsoft account makes it easier to reactivate after hardware changes or reinstallations. To do this, go to Settings > Activation and sign in with your Microsoft account.

Avoid Pirated Activation Tools

While unofficial activation tools may appear convenient, they carry several risks:

  • Potential malware infections or system instability.
  • Inability to receive future updates or official support.
  • Legal risks and violation of Microsoft’s terms of service.
  • The likelihood of being blocked again by future updates.