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.

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.

Design, debug, and test APIs locally or in the cloud

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

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.

Hand-crafted lightweight Rest Client for testing APIs. Supports collections, environments, git collaboration and local storage.