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.

Voiden is a developer-first API client with local storage, Git-integrated, all based on markdown + offline support.

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

ReadyAPI is a low-code API testing platform for development teams that care about creating test automation across any workflow.

Website and mobile testing at every stage of development

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