Swagger UI allows anyone — be it your development team or your end consumers — to visualize and interact with the API’s resources without having any of the implementation logic in place

Fully integrated API and web service testing capabilities that automate end-to-end functional API testing.

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

JustJSON is a free, simple tool that lets developers quickly create, store, and manage JSON collections. Add, retrieve, and delete data with ease—perfect for testing, JSON placeholder, or mocking data for your apps.

Hoppscotch is an open-source API development ecosystem that helps you create and test your API requests saving precious time in development.

Selenium automates browsers. That's it! What you do with that power is entirely up to you.