REST API
Definition & meaning
Definition
A REST API (Representational State Transfer API) is an architectural style for building web services that uses standard HTTP methods — GET, POST, PUT, DELETE — to perform operations on resources identified by URLs. REST APIs are stateless, meaning each request contains all the information needed to process it. They are the most widely used API design pattern on the web, favored for their simplicity and scalability.
How It Works
REST (Representational State Transfer) API is an architectural style for designing networked applications, built on top of HTTP. RESTful APIs organize data into resources, each identified by a unique URL (e.g., /api/users/42). Standard HTTP methods map to CRUD operations: GET retrieves resources, POST creates new ones, PUT/PATCH updates existing ones, and DELETE removes them. Responses include HTTP status codes (200 OK, 201 Created, 404 Not Found, 500 Server Error) and typically return data in JSON format. REST is stateless — each request contains all information needed to process it, with no server-side session state between calls. HATEOAS (Hypermedia as the Engine of Application State) is an advanced REST principle where responses include links to related actions and resources, making the API self-discoverable. Pagination, filtering, sorting, and field selection are handled through query parameters. Caching headers (ETag, Cache-Control) enable efficient data retrieval.
Why It Matters
REST APIs dominate the web. The vast majority of public APIs, SaaS integrations, and backend services follow REST conventions. Understanding REST is a baseline requirement for any developer — it is the lingua franca of web services. For architects, REST's stateless nature enables horizontal scaling and load balancing. For frontend developers, REST endpoints map cleanly to UI data requirements. For API consumers, the predictable structure (resources + HTTP methods + status codes) means you can interact with an unfamiliar REST API quickly if it follows conventions. While GraphQL has gained popularity for specific use cases, REST remains the default choice for most API design decisions due to its simplicity and ubiquity.
Real-World Examples
GitHub's REST API (api.github.com) lets developers programmatically manage repositories, issues, and pull requests. Twitter/X's API, Shopify's Admin API, and Spotify's Web API are all REST-based. On ThePlanetTools.ai, the tools we review predominantly use REST APIs for integration — sending a POST request to generate an image, a GET request to check job status, and a GET to retrieve the result. Supabase auto-generates REST APIs from your PostgreSQL schema via PostgREST. Backend frameworks like Express.js, FastAPI, Django REST Framework, and Rails make building REST APIs straightforward. Tools like Swagger UI provide interactive documentation from OpenAPI specifications.