How to Fix Windows Security That Won't Open
Fix the real Windows Security app when it will not open, shows a blank window, or is blocked by policy without turning protection off.
Windows Security
Microsoft Defender, firewall prompts, and Security that will not open.
Start with the closest symptom
These guides are grouped here because the first checks overlap. Open the guide that best matches what you see now, then use its verification section before moving to a broader fix.
Related tools
- Password Strength Checker, Check password characteristics in your browser. Nothing is sent to our server. This is guidance, not a guarantee.