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.

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

Requestly is an open-source tool that simplifies API development, testing, mocking, and integration for developers and QAs.

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

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

A modern, resource-friendly REST client for Windows 10