Debug Nginx Proxies Layer by Layer

When your Nginx reverse proxy isn’t working, test in this exact order:

Step 1 — Test from the server itself:

curl http://localhost/api

Step 2 — Test via server IP:

curl -k https://SERVER_IP/api

Step 3 — Test via domain:

curl https://yourdomain.com/api

Why this order matters:

• Step 1 fails → Nginx config is broken
• Step 2 fails → SSL certificate issue
• Step 3 fails → DNS, CDN, or firewall issue

I recently debugged a proxy where Step 1 returned perfect responses but Step 3 returned just “OK” (2 bytes). That immediately told me the problem wasn’t Nginx — it was the CDN caching a broken response from an earlier deployment.

Each layer adds complexity. Test each layer separately. When something breaks, you instantly know which layer to investigate instead of guessing.