REST (Representational State Transfer) is an architectural style for designing networked applications, originally defined by Roy Fielding in his 2000 doctoral dissertation. RESTful APIs have become the dominant standard for web service communication, providing a simple, scalable, and stateless approach to building APIs that allow different software systems to exchange data over HTTP. Today, the vast majority of web and mobile applications rely on REST APIs to communicate with backend servers.
RESTful APIs are built around several core principles:
- Resource-based: everything is modeled as a resource identified by a unique URI (e.g., /api/users/123)
- Standard HTTP methods: operations map to HTTP verbs: GET (read), POST (create), PUT (update), PATCH (partial update), DELETE (remove)
- Stateless: each request contains all the information needed to process it; the server maintains no session state between requests
- Uniform interface: a consistent, predictable API design that is easy to understand and use
- Client-server separation: the frontend and backend evolve independently, connected only through the API contract
REST APIs typically use JSON as the data interchange format, though XML and other formats are also supported. Key considerations when designing RESTful APIs include proper HTTP status code usage, versioning strategies, pagination for large datasets, authentication and authorization (often via OAuth2 or JWT tokens), rate limiting, and comprehensive documentation using standards like OpenAPI (Swagger).
While newer alternatives like GraphQL and gRPC have emerged for specific use cases, REST remains the most widely used API architecture due to its simplicity, broad tooling support, and ease of adoption. Designing clean, well-documented RESTful APIs is important for building maintainable, interoperable systems that can serve web, mobile, and third-party clients from a single backend.