RESTfulAPIs

RESTful APIs are web services designed around the constraints of Representational State Transfer (REST). In a RESTful API, each resource is identified by a unique Uniform Resource Identifier (URI), and operations on that resource are performed with standard HTTP methods such as GET, POST, PUT, PATCH, and DELETE. Clients receive resource representations from the server—commonly in JSON or XML—and may supply representations to update resources. REST emphasizes statelessness, so each request contains all necessary information and servers do not retain client context between requests.

Key architectural principles include a uniform interface, statelessness, cacheability, and a layered system. Optional but common is hypermedia as the engine of application state (HATEOAS), where responses include links to subsequent actions. Design patterns typically map CRUD operations to HTTP methods: GET for read, POST for create, PUT or PATCH for update, and DELETE for removal. APIs often implement pagination, filtering, and sorting via query parameters to control large result sets.

Representations are negotiated through content negotiation headers; JSON is the dominant data format, with XML, YAML, or others supported as needed. Security is commonly achieved by using HTTPS, and authentication may rely on tokens, OAuth2, or JWT. Versioning strategies vary, including embedding a version in the URL, using a header, or versioning media types, to preserve backward compatibility as the API evolves.

RESTful APIs offer simplicity, scalability, and loose coupling between client and server, but can require careful design to maintain consistency and discoverability. They contrast with older RPC-style or SOAP-based services by emphasizing resources, statelessness, and standard HTTP semantics.