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Windows Server: How to Reset the Activation Timer

Summary: How to reset the Windows Server activation timer using the slmgr.vbs -rearm command.

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Article Summary: This article provides information on resetting the Windows activation timer using the slmgr.vbs -rearm command.


Every installation of Windows requires activation in order to ensure that licensing requirements are met. Activation takes place automatically in some scenarios, including most volume-activation scenarios, as long as the environment is correctly configured to support it. Other scenarios require manual activation, which typically involves entering the correct product key for the installation of Windows being activated.

In Windows Server 2008 and 2008 R2, activation is not required immediately upon the installation of the operating system. Instead, when Windows is installed on a system, it enters a grace period during which Windows is fully functional without being activated. Activation reminders will appear periodically. When this grace period is over, the activation reminders become more persistent and certain cosmetic changes occur (the desktop background becomes black, for example), but Windows continues to operate normally.

Note: Reduced Functionality Mode (RFM), which was an operating mode of pre-SP1 installations of Windows Vista and pre-release builds of Windows Server 2008 that did not activate within the grace period, is not present in any released version of Windows Server.


Windows Server 2012 and 2012 R2 require that a valid product key be entered during installation. There is no way to bypass this requirement; however, a Key Management System (KMS) client key, also known as a Generic Volume License Key (GVLK), may be entered at the prompt to allow the installation to proceed. GVLKs are used to automatically activate installations of Windows in a KMS environment and are made freely available online by Microsoft.

In an environment in which KMS is not present, the use of a GVLK during installation does not bypass the activation requirement. Windows will periodically attempt to contact a KMS server and will display a watermark on the desktop indicating that it has not been successfully activated:


A GVLK can be a convenient way to utilize Windows Server for a short period of time - for demonstration or training purposes, for example, or in a disaster-recovery or "swing" migration scenario in which a third server is used as a temporary data store between the source and destination server - but it does not provide a permanent activation method in a non-KMS environment.

In all versions since Windows Vista, the activation grace period can be reset by running slmgr.vbs -rearm from an elevated command prompt.


This command typically resets the activation timer to thirty days (sixty in some versions) and can be performed a limited number of times (usually three). Any time remaining in the activation timer is lost when the command is run - in other words, the timer resets to thirty or sixty days regardless of how much time was left previously.

In all cases, despite the fact that the operating system continues to function normally after the end of the grace period, failure to activate Windows is a violation of the applicable Microsoft license agreement.

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Last Published Date

21 Feb 2021



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