Best interactive API documentation tools with live testing (December 2025)
Blog post from Fern
Interactive API documentation is increasingly preferred by developers as it allows them to test API endpoints directly in the browser, facilitating immediate validation of functionality and reducing integration time. Tools like Fern, Scalar, ReadMe, Mintlify, and Stoplight offer different features, such as auto-populated authentication, support for various protocols including REST and WebSocket, and interactive explorers that eliminate the need for external clients like Postman. Fern is highlighted for its comprehensive interactive testing capabilities, integrating both documentation and SDK generation from a single API definition, which ensures synchronization between what developers read and execute. Meanwhile, Scalar and Mintlify are noted for their design flexibility and speed to launch, respectively, although they lack some advanced features like OAuth auto-refresh and multi-protocol support. ReadMe focuses on personalized documentation for public APIs, while Stoplight offers visual tools for API design collaboration but with limited interactive testing features. The overall emphasis is on reducing time-to-first-call by minimizing setup friction and allowing developers to test and trust API behavior more rapidly.