HTTP Methods & Status Codes

🔗 REST API Lesson 2 Beginner

HTTP methods (also called verbs) define the type of action to perform on a resource. HTTP status codes tell the client exactly what happened with their request. Choosing the right verb and status code is the foundation of a well-designed REST API.

1 The Core HTTP Methods

Method	Action	Idempotent?	Has Body?	Example
GET	Read / retrieve a resource	Yes	No	GET /users
POST	Create a new resource	No	Yes	POST /users
PUT	Replace a resource entirely	Yes	Yes	PUT /users/1
PATCH	Partially update a resource	No	Yes	PATCH /users/1
DELETE	Remove a resource	Yes	No	DELETE /users/1
HEAD	GET without response body	Yes	No	HEAD /users
OPTIONS	List allowed methods (CORS preflight)	Yes	No	OPTIONS /users

2 HTTP Status Code Groups

Range	Category	Common Codes
1xx	Informational	100 Continue, 101 Switching Protocols
2xx	Success	200 OK, 201 Created, 204 No Content
3xx	Redirection	301 Moved Permanently, 304 Not Modified
4xx	Client Errors	400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found, 409 Conflict, 422 Unprocessable, 429 Too Many Requests
5xx	Server Errors	500 Internal Server Error, 502 Bad Gateway, 503 Service Unavailable

3 Correct Method & Status Mapping

HTTP — REST Method Examples

# List all users
GET /api/users             -> 200 OK  (with array body)

# Create user
POST /api/users            -> 201 Created  (with new resource body)

# Get specific user
GET /api/users/42          -> 200 OK  |  404 Not Found

# Full replace
PUT /api/users/42          -> 200 OK  (with updated body)

# Partial update
PATCH /api/users/42        -> 200 OK  (with updated body)

# Delete — returns NO body
DELETE /api/users/42       -> 204 No Content

# Bad request body
POST /api/users            -> 400 Bad Request  (missing required fields)

# No token
GET /api/admin             -> 401 Unauthorized

# Valid token, wrong permissions
GET /api/admin             -> 403 Forbidden

4 Code Challenge

Challenge: Using curl or Postman, test all 5 CRUD operations against https://jsonplaceholder.typicode.com/posts and record the HTTP method, URL, request body (if any), and the response status code for each.