I've lost count of how many times I've spent hours debugging an API integration, only to realize the issue wasn't my code, but a silent 502 Bad Gateway or a misconfigured Content-Type header.

When a web application fails silently, the first thing you should do is look at the raw HTTP response. Browsers abstract this away from us, so as developers, we need to drop down to the network layer.

Here is my standard workflow for debugging APIs using cURL, and how to do it faster when you don't have terminal access.

The Basics: Fetching Headers Only When debugging, you usually don't care about the entire HTML body. You just want the headers. Using -I (or --head) tells cURL to only fetch the headers:

bash

curl -I https://api.example.com/v1/users

This will return the HTTP status code (200, 404, 500), the server type, cache control, and crucially, the Content-Type.

Following Redirects (301 vs 302) If you are migrating a site or testing an API endpoint, you need to know if the server is redirecting you.…