MARS-Curiosity is a popular open-source REST library for Embarcadero Delphi. It provides to Delphi developers an easy and familiar path to build REST applications (supporting both sides: server and client).
The philosophy behind the project is to keep the REST layer as small as possible, enabling easy plug-in of other technologies (data access libraries, serialization frameworks, ORM, document producers, …). The library provides easy access to Delphi-to-Delphi advantages (including FireDAC integration for datasets, including delta operations, and other design-time capabilities) but always keeping an eye to actual interoperability (standard JSON representations).
This session will provide an overview of the new features (v.1.4 and later).

https://github.com/andrea-magni/MARS