As you navigate the web, you’ll encounter various HTTP status codes. These codes are responses from the server indicating the status of a specific HTTP request. Understanding these codes is crucial for diagnosing and fixing issues in web development. Here’s a guide to the most common HTTP status codes and what they mean.

1. 200 OK

The request has succeeded. The information is returned with the response.

2. 201 Created

The request has been fulfilled, resulting in the creation of a new resource. This is typically the response sent after a POST request.

3. 301 Moved Permanently

The resource requested has been permanently moved to a new URL. The new URL is provided in the response.

4. 400 Bad Request

The server cannot or will not process the request due to something that is perceived to be a client error (e.g., wrong request syntax).

5. 401 Unauthorized

The request requires user authentication. The response must include a proper authentication.

6. 403 Forbidden

The server understood the request, but refuses to authorize it. A 403 status code indicates that the server can be reached and understood the request, but refuses to take any further action.

7. 404 Not Found

The server can't find the requested resource. This code is commonly used when the server doesn't want to reveal whether it has the resource or not.

8. 500 Internal Server Error

The server encountered an unexpected condition that prevented it from fulfilling the request. This is a generic error message, given when no more specific message is suitable.

9. 502 Bad Gateway

The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting to fulfill the request.

10. 503 Service Unavailable

The server is currently unable to handle the request due to temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay.

To make it easier to remember some of these codes, here’s a handy cheatsheet graphic: