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.

Create automatic monitors for detecting and scanning changes on web pages, evaluate content based on conditions you define and trigger actions such as notifications, sounds, emails etc.

REST API client library for .NET

Puppeteer is a Node.js library which provides a high-level API to control Chrome/Chromium over the DevTools Protocol.

Test, scrape, generate, and automate without the pain and expense of hosting your own headless browsers.

RapidAPI for Mac is a full-featured HTTP client that lets you test and describe the APIs you build or consume. It has a beautiful native macOS interface to compose requests, inspect server responses, generate client code and export API definitions.