I’ve had to go look for this information twice this month, both times struggling to remember how I found the information, so it seems only right to blog the answer as well as the link for both myself and anyone who is searching for it.
The below table lists all the KMS installation keys for Windows 8.1 and Windows Server 2012 R2. You can use these keys to complete an installation of Windows and also to activate an already installed instance.
| Operating system edition | KMS Client Setup Key |
|---|---|
| Windows 8.1 Professional | GCRJD-8NW9H-F2CDX-CCM8D-9D6T9 |
| Windows 8.1 Professional N | HMCNV-VVBFX-7HMBH-CTY9B-B4FXY |
| Windows 8.1 Enterprise | MHF9N-XY6XB-WVXMC-BTDCT-MKKG7 |
| Windows 8.1 Enterprise N | TT4HM-HN7YT-62K67-RGRQJ-JFFXW |
| Windows Server 2012 R2 Server Standard | D2N9P-3P6X9-2R39C-7RTCD-MDVJX |
| Windows Server 2012 R2 Datacenter | W3GGN-FT8W3-Y4M27-J84CP-Q3VJ9 |
| Windows Server 2012 R2 Essentials | KNC87-3J2TX-XB4WP-VCPJV-M4FWM |
In the source link below you can find the KMS keys for the following operating systems:
- Windows Server 2012 R2 and Windows 8.1 Client Setup Keys
- Windows Server 2012 and Windows 8 Client Setup Keys
- Windows 7 and Windows Server 2008 R2
- Windows Vista and Windows Server 2008
Source: http://technet.microsoft.com/en-us/library/jj612867.aspx
Deployment Pros 
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hello, thanks, but the win server 2012 r2 key is not working
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thanks bro but win server 2012 r2 is not working