Best Developer Tools for API Testing Online (2024)

API testing is a daily ritual for most developers. Whether you're verifying a new endpoint, debugging a 401 response, or checking what a third-party API actually returns — you need a fast, reliable tool to fire HTTP requests and inspect responses. The good news: the best API testing tools are free. This guide compares the top options available online and locally, so you can pick the right one for your workflow. What Makes a Good API Testing Tool? Before comparing tools, here's what actually matters: Speed to first request : How fast can you go from "I need to test this endpoint" to seeing a response? Request flexibility : Can you set custom headers, auth tokens, request bodies? Response inspection : Is the response JSON formatted and readable? Can you see headers and status codes? Collections/History : Can you save and organize requests for reuse? Collaboration : Can you share requests with teammates? Different tools optimize for different points on this list. 1. DevPlaybook API Tester