Checklists for software errors, setup, and tool workflows.

1. Reproduce

2. Isolate

3. Apply

4. Verify

Latest checklists

If you see ! [rejected] and non-fast-forward when running git pus...

How to Fix Nginx Redirect Loop with Cloudflare
You set up Cloudflare for your site, and now visitors see a redirect loop error. The page keeps r...

Fix Nginx Upstream Connection Refused in Proxy Pass
When Nginx returns a 502 Bad Gateway or logs upstream connection refused

Fixing Nginx Upstream Connection Refused and Permission Denied
If you see connect() failed (111: Connection refused) or connect() failed (13:...

Fixing Python UnicodeDecodeError When Reading UTF-16 Files
You open a file in Python and get UnicodeDecodeError: 'utf-8' codec can't decod...

Fix Cloudflare 521 Error: SSL Configuration Steps
If you see a Cloudflare 521 error, it means Cloudflare can't establish a TCP connection to yo...