Postman is an API platform for building and using APIs. Postman simplifies each step of the API lifecycle and streamlines collaboration so you can create better APIs—faster.

Bruno is a Fast and Git-Friendly Opensource API client, aimed at revolutionizing the status quo represented by Postman, Insomnia and similar tools out there.

A modern, resource-friendly REST client for Windows 10

Clippy lets you run a variety of large language models (LLMs) locally on your computer while sticking with a user interface of the 1990s. It's a love letter and homage to the late, great Clippy - and the visual design created by Microsoft in that era.

API Testing Platform that automatically generates unit test cases with dependency mocks from API calls

Burp or Burp Suite is a set of tools used for penetration testing of web applications. It is developed by a company named Portswigger who make freely available a Web Security Academy which has a range of lessons on penetration testing.