Skip to main content

Understanding HTTP status codes

HTTP status codes are server responses to client requests made over HTTP, and they play a crucial role in understanding the communication between the client and the server. Let's dive in and learn more about them.

What are HTTP Status Codes?​

HTTP (Hypertext Transfer Protocol) status codes are three-digit numbers that are returned by servers to indicate the status of a web elements, such as a page or a resource. They are part of the HTTP/1.1 standard, and they are divided into five classes or categories.

Classification of HTTP Status Codes​

HTTP status codes are divided into five classes:

  1. 1xx (Informational): The request was received, and the process is continuing.
  2. 2xx (Successful): The request was successfully received, understood, and accepted.
  3. 3xx (Redirection): Further actions must be taken in order to complete the request.
  4. 4xx (Client Error): The request contains bad syntax or cannot be fulfilled.
  5. 5xx (Server Error): The server failed to fulfill an apparently valid request.

Common HTTP Status Codes​

Let's go through some commonly encountered HTTP status codes:

1. 200 OK​

This is the most common code that indicates a successful HTTP request. The request has succeeded, and the requested information is returned in the response.

2. 301 Moved Permanently​

This status code means that the URL of the requested resource has permanently changed. The new URL will be given in the response.

3. 400 Bad Request​

This status code indicates that the server could not understand the request due to invalid syntax.

4. 401 Unauthorized​

This status code means that authentication is required to get the requested response. This is similar to 403 (Forbidden), but specifically for cases where authentication is required and has failed or not yet been provided.

5. 404 Not Found​

This status code is perhaps the most well-known. It indicates that the server can't find the requested resource.

6. 500 Internal Server Error​

This is a generic error message when an unexpected condition was encountered by the server and no more specific message is suitable.

What to do when encountering these codes?​

When you encounter these status codes, understanding their meaning helps you to troubleshoot. For instance, if you get a 404 error, you know the requested resource is not available, and you need to check the resource's existence. Similarly, a 500 error might mean something is wrong on the server side.

Conclusion​

Understanding HTTP status codes is fundamental when working with web technologies. These codes provide a standard way for servers to communicate the status of a request to the client, and thus, a basic understanding of what these codes mean can greatly assist when debugging and developing web applications. The complete list of HTTP status codes can be found in the HTTP/1.1 specification.

Remember, understanding them won't just help you in handling errors and exceptions, but will provide you with a better grasp of how the web works under the hood.