Rest.li is an open-source framework developed by LinkedIn for building scalable and robust RESTful APIs. It facilitates the creation, management, and consumption of APIs while promoting best practices in API design. The framework supports features such as automatic data serialization, client-side code generation, and a flexible data model, making it suitable for high-performance applications. Rest.li is designed to handle complex data interactions and is widely used within LinkedIn and by other organizations seeking to streamline their API development processes.