HTTP and URL tools

Debugging an API often starts with text copied from a terminal, browser DevTools or a log. It might be a cURL command, a block of response headers, a long URL with a query string or a bearer token. These tools turn that text into structured data you can read and compare.

A few rules explain most surprises. HTTP header names are case-insensitive, and some fields, such as Set-Cookie, can appear more than once. Query strings have no single standard for repeated keys, so ?tag=a&tag=b may reach your server as an array, the last value or the first value, depending on the framework. In form encoding a + means a space, while in a URL path it is a literal plus sign. A signed JWT's payload is only Base64url-encoded, not encrypted, so anyone with the token can read its claims.

Convert a cURL command to fetch, Python requests or Go code, or inspect its method, URL, headers, body and auth flags without running it. Turn a raw header block into JSON, break a URL into its parts, parse or build query strings, and URL encode values correctly. Look up the MIME type and Content-Type value for a file extension, or decode a JWT to check its claims and expiry. Nothing you paste is sent anywhere. Parsing happens in your browser.