Bruno is a Fast and Git-Friendly Opensource API client, aimed at revolutionizing the status quo represented by Postman, Insomnia and similar tools out there.

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.

Postman is an API platform for building and using APIs. Postman simplifies each step of the API lifecycle and streamlines collaboration so you can create better APIs—faster.

Free & OpenSource REST API Testing Tool for all levels in a Test Pyramid

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

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