Product activation is required for all editions of Windows 10. Windows activation keys and methods are in place to ensure that PC users’ copy of Windows is properly licensed.

Windows PC users are required by the Windows License Terms to activate their copies of Windows to use the operating system.

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Section 5: Authorized Software and Activation. You are authorized to use this software only if you are properly licensed and the software has been properly activated with a genuine product key or by other authorized method.

Depending on how you got your copy of Windows 10, you’ll need either a digital license or a 25-character product key to activate it. Without one of these, you won’t be able to activate your device.

Activation occurs when you connect to the Internet while using the software, the software will automatically contact Microsoft or its affiliate to conduct activation to associate it with a certain device. During activation (or reactivation that may be triggered by changes to your device’s components), the software may determine that the installed instance of the software is counterfeit, improperly licensed or includes unauthorized changes. If activation fails, you’ll receive an error message and also an error code.

Some of the most common activation errors with possible solutions for Windows 10, is available here.