Insomnia

Insomnia is a powerful, elegant, and open-source API client that has gained a strong following as a streamlined alternative to Postman. Acquired by Kong Inc., it focuses on a superb developer experience for designing, debugging, and testing REST, GraphQL, gRPC, and SOAP APIs. Its interface is clean and fast, with excellent support for environment variables, code generation, and plugin extensions. The core app is free, with paid Syncing features for teams.

It shines in its simplicity and speed for day-to-day API interaction and test suite creation. Insomnia is ideal for individual developers and small teams who prioritize a fast, uncluttered, and locally-focused tool for API development and testing, without the platform-heavy approach of its main competitor.