Mock and modify HTTP request for exploratory testing.

Mockoon is the easiest and quickest way to design and run mock REST APIs.

Real API Design-first Development Platform Design. Debug. Test. Document. Mock. Build APIs Faster & Together.

Loader.io is a free load testing service that allows you to stress test your web-apps & apis with thousands of concurrent connections.

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.

Comprehensive and user-friendly cloud platform for Load Testing, Speed Testing and Website & API Optimization and Monitoring