Activation 4 min· Updated 2026-10-16
How to Activate Windows 11 (or 10) with a Product Key
Step-by-step activation via Settings, slui, and command line — plus what to do when activation fails.
A 25-character product key activates Windows in seconds when everything matches: the key's edition must match the installed edition (a Pro key won't activate Home). Here are the three ways to do it.
Method 1: Settings (easiest)
- •Open Settings → System → Activation
- •Click "Change product key"
- •Paste the 25-character key → Next
- •Windows connects to activation servers and you're done
Method 2: slui.exe
- •Press Win+R, type slui 3, press Enter
- •Enter the key in the activation window → Activate
Method 3: Command line (slmgr)
:: Run as Administrator slmgr /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX :: install the key slmgr /ato :: activate online slmgr /xpr :: check activation status
If activation fails
- •Edition mismatch — a Pro key cannot activate Home (the #1 cause). Check your edition: Settings → System → About.
- •Error 0xC004C008 / 0xC004C020 — key already in use or activation limit reached.
- •Error 0xC004F050 — key is for a different edition/channel.
- •No internet? Use phone activation: slui 4 (works with MAK keys).
Verify before you install
You can check what edition and channel a key belongs to before installing — paste it into our free PID Checker to see exactly what it activates.
Check a key or find your license
Free tools — no account needed.