REST (Representational State Transfer) is an architectural style for designing networked applications. REST APIs use standard HTTP methods and status codes to enable communication between clients (web applications, mobile apps, or other services) and servers.
REST was introduced by Roy Fielding in 2000 and has become the dominant approach for building web services and APIs.
REST Principles
Client-Server Architecture: Clients and servers are separate. Clients request data; servers process requests and respond.
Statelessness: Each request contains all information needed to understand it. Servers do not store client context between requests. This simplifies scaling.
Uniform Interface: All clients interact with servers using the same interface. This universality enables any client to interact with any server.
Resource-Based: REST APIs model entities as resources with unique identifiers (URLs). Instead of defining actions, REST defines operations on resources.
Representation: Resources are represented in various formats (JSON, XML). Clients request representations they can process.
HTTP Methods in REST
GET: Retrieves a resource without modifying it. Multiple identical GET requests return the same result (idempotent).
POST: Creates a new resource. POST requests may have side effects and are not idempotent.
PUT: Replaces an entire resource. Multiple identical PUT requests result in the same state (idempotent).
PATCH: Partially updates a resource.
DELETE: Removes a resource. Multiple identical DELETE requests result in the same state (idempotent).
HTTP Status Codes
2xx Success: 200 (OK) indicates success. 201 (Created) indicates a resource was created.
3xx Redirection: 301 (Moved Permanently) and 302 (Found) redirect clients.
4xx Client Error: 400 (Bad Request) indicates invalid request. 401 (Unauthorized) indicates authentication is required. 403 (Forbidden) indicates insufficient permissions. 404 (Not Found) indicates the resource does not exist.
5xx Server Error: 500 (Internal Server Error) indicates server failure.
REST API Naming Conventions
Good REST APIs follow consistent naming conventions. Plural nouns represent resource collections. For example, /users represents all users. /users/123 represents the user with ID 123.
Verbs in URLs should be avoided. Instead of /users/123/delete, use DELETE /users/123.
JSON Responses
Most modern REST APIs respond with JSON. JSON is human-readable and programming language-independent.
{
"id": 1,
"name": "John Smith",
"email": "john@example.com"
}Pagination
APIs returning large collections use pagination. Clients request specific pages, reducing response sizes.
{
"page": 1,
"per_page": 20,
"total": 500,
"data": [...]
}Filtering and Sorting
APIs allow filtering results. /users?role=admin returns only admin users. APIs support sorting. /users?sort=name orders users alphabetically.
Versioning
REST APIs use versioning as they evolve. /v1/users and /v2/users allow supporting old and new API versions simultaneously.
Authentication
REST APIs use various authentication mechanisms. API keys are simple tokens. OAuth 2.0 is industry-standard for delegated access. JWT tokens encode user information.
Rate Limiting
Preventing abuse, APIs limit requests from individual clients. Rate limits are typically returned in response headers.
HATEOAS
Some REST APIs include links to related resources, enabling clients to discover functionality without memorising URLs. This advanced concept improves API discoverability.
REST vs. RPC
REST contrasts with RPC (Remote Procedure Call) style APIs. RPC style calls functions on remote servers. REST style operates on resources. REST's uniform interface is a significant advantage.
PixelForce's REST API Development
PixelForce builds REST APIs using Ruby on Rails. Our APIs follow REST principles, enabling diverse clients to interact with our backends.
REST API Testing
REST APIs are easily tested using tools like Postman or curl. Clear naming and HTTP semantics make testing straightforward.
The Evolution of REST
Whilst REST remains dominant, alternatives like GraphQL address specific limitations. REST APIs will likely remain the most common approach for years.