Part 1: Check your Windows edition (before you buy or activate)

1
On your keyboard, press Windows + R. A small Run box opens. Type winver and click OK.
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2
A box shows your Windows version. Read the line that says Windows 11 Pro, Windows 11 Home (or 10). A Pro key works on Pro, and also upgrades Home to Pro.
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Part 2: Enter your key

3
Open Settings (press Windows + I). Click System, then scroll down and click Activation.
Windows 10: Settings → Update & Security → Activation.
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4
Next to Change product key, click Change.
5
Type the 25-character key we sent you (no need to type the dashes) and click Next, then Activate.
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You're done when:

Wait about a minute. The Activation page now says Active (Windows 11) or Windows is activated (Windows 10).

1
Press Windows + R, type slmgr /dli and click OK. A box shows RETAIL channel and Licensed.
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“This product key didn't work”: Check the edition with winver. Make sure you typed the key correctly and the PC is online, then try again. Still stuck? Send us a screenshot.
It says “Windows Home”, but I bought Pro: That's fine. Entering the Pro key upgrades Home to Pro. The PC restarts once and your files stay.
Installing Windows from scratch: Download Windows from our Downloads page (official Microsoft links). During setup, enter the key or choose “I don't have a product key” and activate afterwards with the steps above.