200 OK and 201 Created in Rest API

Introduction

These status codes tell you if your request to a web server worked. They help you understand what happened after you sent data or asked for something.

When you successfully get data from a server, like loading a webpage or fetching user info.

When you send new data to a server and it creates something new, like signing up for a new account.

When you update existing data and want to confirm it worked without creating anything new.

When you want to know if your request was successful and what kind of success it was.

Syntax

Rest API

HTTP/1.1 200 OK

HTTP/1.1 201 Created

200 OK means the request was successful and the server sent back the requested data or confirmation.

201 Created means the request was successful and the server created a new resource as a result.

Examples

This shows a successful response with data sent back to the client.

Rest API

HTTP/1.1 200 OK
Content-Type: application/json

{"name": "Alice", "age": 30}

This shows a new user was created and the server tells where to find it.

Rest API

HTTP/1.1 201 Created
Location: /users/123

{"id": 123, "name": "Bob"}

Sample Program

This simple web server has two routes: one to get all users with a 200 OK response, and one to add a new user with a 201 Created response.

Rest API

from flask import Flask, jsonify, request

app = Flask(__name__)

users = []

@app.route('/users', methods=['GET'])
def get_users():
    return jsonify(users), 200

@app.route('/users', methods=['POST'])
def create_user():
    user = request.json
    user['id'] = len(users) + 1
    users.append(user)
    return jsonify(user), 201

if __name__ == '__main__':
    app.run(debug=True)

Important Notes

Use 200 OK when you return data or confirm a successful action without creating new resources.

Use 201 Created when your request results in a new resource being made on the server.

Always include useful information in the response body or headers to help the client understand what happened.

Summary

200 OK means success and data or confirmation is sent back.

201 Created means success and a new resource was created.

These codes help clients know how their requests were handled.

Practice

1. What does the HTTP status code 200 OK indicate in a REST API response?

easy

A. A new resource was successfully created on the server.

B. The request was successful and the server is returning the requested data or confirmation.

C. The client made a bad request and the server could not understand it.

D. The server encountered an error and could not complete the request.

Solution

1. Step 1: Understand the meaning of 200 OK

   The status code 200 OK means the request was successful and the server is sending back the requested data or confirmation.

2. Step 2: Compare with other codes

   201 Created means a new resource was created, which is different from 200 OK.

3. Final Answer:

   The request was successful and the server is returning the requested data or confirmation. -> Option B

4. Quick Check:

   200 OK = Success with data [OK]

Hint: 200 OK means success with data returned [OK]

Common Mistakes:

• Confusing 200 OK with 201 Created
• Thinking 200 means resource creation
• Mixing 200 with client or server error codes

2. Which of the following is the correct way to indicate a successful creation of a new resource in a REST API response?

easy

A. HTTP/1.1 201 Created

B. HTTP/1.1 404 Not Found

C. HTTP/1.1 500 Internal Server Error

D. HTTP/1.1 200 OK

Solution

1. Step 1: Identify the status code for resource creation

   The status code 201 Created is used when a new resource is successfully created on the server.

2. Step 2: Eliminate incorrect options

   200 OK means success but not necessarily creation; 404 and 500 are error codes.

3. Final Answer:

   HTTP/1.1 201 Created -> Option A

4. Quick Check:

   201 Created = New resource created [OK]

Hint: Use 201 Created for new resource success [OK]

Common Mistakes:

• Using 200 OK instead of 201 for creation
• Confusing 404 Not Found as success
• Mixing error codes with success codes

3. Consider this REST API response code snippet:

HTTP/1.1 201 Created
Location: /users/123

{"id":123,"name":"Alice"}

What does this response tell the client?

medium

A. The client made a bad request and should try again.

B. The request failed and no resource was created.

C. The server is returning existing user data without creating anything new.

D. A new user resource was created with ID 123, and its location is provided.

Solution

1. Step 1: Analyze the status code 201 Created

   This code means a new resource was successfully created on the server.

2. Step 2: Interpret the Location header and response body

   The Location header shows where the new resource is located (/users/123), and the body contains the new user's data.

3. Final Answer:

   A new user resource was created with ID 123, and its location is provided. -> Option D

4. Quick Check:

   201 Created + Location header = New resource created [OK]

Hint: 201 with Location means new resource created [OK]

Common Mistakes:

• Ignoring the Location header
• Thinking 201 means failure
• Confusing 201 with 200 OK

4. You wrote a REST API endpoint to create a new product. The server returns 200 OK instead of 201 Created. What is the likely issue?

medium

A. The server did not create a new resource but only confirmed the request.

B. The client sent an invalid request format.

C. The server successfully created the resource but forgot to set the correct status code.

D. The server encountered an internal error while creating the resource.

Solution

1. Step 1: Understand the difference between 200 OK and 201 Created

   200 OK means success but not necessarily resource creation; 201 Created explicitly means a new resource was created.

2. Step 2: Analyze the server behavior

   If the resource was created but 200 OK was returned, the server likely forgot to set the correct status code.

3. Final Answer:

   The server successfully created the resource but forgot to set the correct status code. -> Option C

4. Quick Check:

   201 Created must be set on resource creation [OK]

Hint: 201 must be set when resource is created [OK]

Common Mistakes:

• Assuming 200 OK means creation
• Ignoring status code importance
• Confusing client errors with server response codes

5. You are designing a REST API for a blog. When a new post is created, you want to return the correct status code and the URL of the new post. Which response is the best practice?

hard

A. Return 201 Created with the Location header set to the new post URL and the post data in the body.

B. Return 404 Not Found because the post did not exist before.

C. Return 200 OK with the post data in the body but no Location header.

D. Return 500 Internal Server Error to indicate the server created the post.

Solution

1. Step 1: Identify the correct status code for resource creation

   201 Created is the standard code to indicate a new resource was successfully created.

2. Step 2: Use the Location header to provide the new resource URL

   Including the Location header with the new post URL helps clients find the resource easily.

3. Final Answer:

   Return 201 Created with the Location header set to the new post URL and the post data in the body. -> Option A

4. Quick Check:

   201 Created + Location header = Best practice for new resource [OK]

Hint: Use 201 Created + Location header for new resources [OK]

Common Mistakes:

• Returning 200 OK without Location header
• Using error codes for successful creation
• Not including the new resource URL