REST API Introduction — Representational State Transfer Explained

In this tutorial, you will learn about REST API Introduction. We cover key concepts, practical examples, and best practices to help you master this topic.

REST (Representational State Transfer) is the most widely adopted architectural style for web APIs, using standard HTTP methods to perform operations on resources identified by URIs in a stateless manner.

What You'll Learn

• The six REST constraints and why each one matters
• How HTTP methods map to CRUD operations
• Why REST became the dominant Api Design standard

Why It Matters

Most public APIs you use are RESTful. Understanding REST is essential for backend development, frontend integration, and API design.

flowchart LR
    A["REST API"] --> B["Resources\n(URIs)"]
    A --> C["HTTP Methods\nGET, POST, PUT, DELETE"]
    A --> D["Statelessness"]
    A --> E["Cacheable Responses"]
    B --> F["JSON Representation"]
    C --> G["CRUD Operations"]
    style A fill:#dbeafe,stroke:#2563eb

Code Examples

import requests

# RESTful API calls
base = "https://jsonplaceholder.typicode.com"

# GET - read resource
response = requests.get(f"{base}/posts/1")
print("GET:", response.status_code, response.json()["title"])

# POST - create resource
new_post = {"title": "My Post", "body": "Content", "userId": 1}
response = requests.post(f"{base}/posts", json=new_post)
print("POST:", response.status_code, response.json()["id"])

# RESTful API with curl
curl -X GET https://jsonplaceholder.typicode.com/posts/1
curl -X POST https://jsonplaceholder.typicode.com/posts \
  -H "Content-Type: application/json" \
  -d '{"title":"My Post","body":"Content","userId":1}'

Common Mistakes

1. Thinking REST is Just CRUD Over HTTP

REST is an architectural style, not a database wrapper.

2. Ignoring Statelessness

Storing session state on the server breaks REST constraints.

3. Using Verbs in URIs

Use /users not /getUsers. HTTP methods are the verbs.

4. Not Using HTTP Status Codes Properly

Return 201 for creation, 204 for deletion, 400 for bad requests.

5. Overlooking HATEOAS

REST responses should include links to related resources for discoverability.

Practice Questions

1. What does REST stand for?
2. How many constraints define a RESTful system?
3. What is the difference between PUT and PATCH?
4. Why must REST APIs be stateless?
5. What is the uniform interface constraint?

Answers:

1. Representational State Transfer.
2. Six constraints (client-server, statelessness, cacheability, uniform interface, layered system, code on demand).
3. PUT replaces the entire resource; PATCH applies a partial update.
4. Statelessness enables horizontal scaling without session synchronization.
5. Resources are identified by URIs, manipulated through representations, and include self-descriptive messages.

Challenge: Design a RESTful API for a library with endpoints for books, members, and loans. Show the HTTP methods, URIs, and expected status codes for each operation.

FAQ

What's Next

Learn about RESTful Resources and URI design, or compare REST with SOAP and GraphQL.