If you’re working with Windows Server, understanding licensing is crucial. By default, Windows Server installations come with a 180-day trial period. Once this period expires and if no licensing action is taken your servers will begin shutting down.
Fortunately, Microsoft provides the Software License Manager (SLMGR) utility, a powerful command-line tool for:
- Installing or changing product keys
- Activating Windows
- Extending the trial period
- Managing KMS (Key Management Service) settings
- Checking License Information
Display Basic License Details
To view essential licensing information such as your Windows Server edition, partial product key, license status, and activation expiration run:
slmgr /dli
View Detailed License Information
For more in-depth details, including the remaining Windows rearm count (which determines how many times you can extend the trial), use:
slmgr /dlv
Extending the Windows Server Trial Period
By default, Windows Server provides:
- 180 days of initial trial usage
- 5 rearm attempts (allowing you to reset the activation timer)
This means you can effectively use Windows Server for: 5 × 180 days = 900 days (~2.4 years) without purchasing a license.
How to Reset the Trial Period
When your activation timer nears expiration, you can reset it by running:
slmgr /rearm
After executing this command, a system restart is required. Each use of /rearm decrements your remaining rearm count.