Checklists for software errors, setup, and tool workflows.

1. Reproduce

2. Isolate

3. Apply

4. Verify

Latest checklists

When Nginx returns a 502 Bad Gateway or logs upstream connection refused

How to Fix ERR_CONNECTION_RESET on Chrome Mobile
When browsing on your phone, you might see the error ERR_CONNECTION_RESET in Chr...

Fix NET::ERR_CERT_AUTHORITY_INVALID in Chrome Safe Mode
When you see NET::ERR_CERT_AUTHORITY_INVALID in Chrome while running in Safe Mod...

Cloudflare Origin Certificate Setup Checklist
You've set up Cloudflare but your origin server still shows SSL errors or mixed content warni...

Fix Node.js Heap Out of Memory When Loading Modules
If you see FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaS...

Fix Cloudflare Error 521 After a Server Update
If you see Cloudflare error 521 after updating your server, the origin web server is refusing the...