How to Fix Cloudflare 521 Error with Firewall Settings
If you see a 521 Web Server Is Down error when visiting your site through Cloudf...
Checklists for software errors, setup, and tool workflows.
1. Reproduce
2. Isolate
3. Apply
4. Verify
Latest checklists
View listFix Windows Update Error 0x80070002 on Windows 11
If you see error 0x80070002 when running Windows Update on Windows 11, it usually means Windows c...
How to Fix Firefox Secure Connection Failed Certificate Error
You see a full-page error in Firefox: Secure Connection Failed with a message li...
Fix pnpm ERR_PNPM_OUTDATED_LOCKFILE Lockfile Error
When running pnpm install or pnpm update, you may see:
ER...Fix Node.js package.json Engine Check Failures
When you run npm install and see an error like EBADENGINE or engi...
Nginx Upstream Connection Refused: Diagnosis and Fixes
When Nginx returns a 502 Bad Gateway or logs "upstream connection refused", it means Ngin...
Topic paths
Quick titles
DNS Propagation Troubleshooting for Cloudflare UsersTroubleshooting Cloudflare 521 Error After DNS ChangeHow to Force Enable Windows Defender Real-Time ProtectionCommon Git LFS Push Failures and How to FixHow to Create a Python Virtual Environment for Externally Managed ErrorTroubleshooting Cloudflare Error 522: Step-by-StepFix Chrome Hardware Acceleration Black Screen in Windows 11Nginx Permission Denied: Fix www-data User Access