HTTP Status Codes Explained: Complete Guide to 1xx, 2xx, 3xx, 4xx, 5xx with Examples

If you have ever developed or used an API, you have undoubtedly encountered HTTP Status Codes. When you get responses like 200 OK or 404 Not Found, those are the three digit numbers. However, what do they actually mean? And what makes them so crucial?

For web developers, backend engineers and students looking to advance their knowledge of APIs and the web, this blog will simplify and make HTTP Status Codes easy to understand.

What Are HTTP Status Codes?

HTTP Status Codes are standardized response codes given by web servers when you make a request. They tell you whether your request was successful, failed or needs further action.

👉 Example: When you type a URL in your browser, the server responds with a status code before delivering the page.

• If it is 200 OK, everything went fine
• If it is 404 Not Found, the server couldn’t find the page

Categories of HTTP Status Codes

HTTP status codes are grouped into five categories based on their first digit:

1xx – Informational

These indicate that the request was received and the process is continuing.

• 100 Continue – Request received continue the process.
• 101 Switching Protocols – Protocol switching (e.g. HTTP to WebSocket)

2xx – Success ✅

These mean the request was successfully received, understood and accepted

• 200 OK – Standard success response
• 201 Created – A new resource has been successfully created
• 204 No Content – Request succeeded but no content is returned

3xx – Redirection 🔁

These indicate the client must take additional steps to complete the request.

• 301 Moved Permanently – Resource has been permanently moved to a new URL
• 302 Found – Temporary redirection
• 304 Not Modified – Resource has not changed since last request (used for caching)

4xx – Client Errors ❌

These indicate a problem with the request sent by the client.

• 400 Bad Request – Invalid request syntax
• 401 Unauthorized – Authentication required
• 403 Forbidden – The client is not allowed to access the resource
• 404 Not Found – Resource not found
• 429 Too Many Requests – You have hit the rate limit

5xx – Server Errors ⚠️

These indicate that the server failed to fulfill a valid request.

• 500 Internal Server Error – Generic server error
• 502 Bad Gateway – Invalid response from an upstream server
• 503 Service Unavailable – Server is temporarily down or overloaded
• 504 Gateway Timeout – Server took too long to respond

🌍 Why Are HTTP Status Codes Important?

• Debugging: They help developers quickly identify what went wrong
• SEO: Search engines like Google pay attention to HTTP status codes (e.g. 404 errors harm rankings)
• User Experience: Correct status codes improve app reliability

👉 For example: instead of showing a blank page a 404 page should guide users back to the homepage.

Practical Example

Request:

GET /api/users HTTP/1.1
Host: example.com

Response:

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

{
  "users": [
    {"id": 1, "name": "Alice"},
    {"id": 2, "name": "Bob"}
  ]
}

👉 If the endpoint did not exist you would get:

HTTP/1.1 404 Not Found

Best Practices for Using HTTP Status Codes

• Always return the most accurate status code
• Don’t misuse 200 OK for every response
• Use 201 Created when creating resources
• Implement custom error pages for 404 and 500 errors
• Use 429 Too Many Requests to handle rate limiting

Key Takeaways

• HTTP status codes are the language of communication between clients and servers
• They’re divided into five categories (1xx to 5xx)
• Correct use of status codes improves debugging, SEO and user experience

Final Thoughts

Whether you are just starting with web development or working on advanced APIs, mastering HTTP Status Codes is essential. They make your applications more reliable, SEO friendly and user friendly.

✅ Next time you debug an API, check the status code first