HTTP status codes are three-digit numbers returned by servers to indicate the status of a web request. These codes give information about whether a request was successful, if there were errors, or other types of responses. Here’s a breakdown of the various classes of HTTP status codes and some of their commonly used codes:

1. 1xx (Informational):

These codes indicate that the request was received and is being processed.

• 100 Continue: The initial part of the request has been received, and the client may continue.
• 101 Switching Protocols: The server will switch to another protocol as requested by the client.

2. 2xx (Successful):

These codes indicate that the request was successfully received, understood, and accepted.

• 200 OK: The request was successful.
• 201 Created: The request was successful, and a resource was created.
• 202 Accepted: The request was accepted but hasn’t been processed yet.
• 204 No Content: The request was successful, but there’s no representation to return (i.e., the response is empty).

3. 3xx (Redirection):

These codes indicate that further action needs to be taken by the user agent to fulfill the request.

• 300 Multiple Choices: Multiple options for the resource that the client may follow.
• 301 Moved Permanently: The resource has been permanently moved to a new location.
• 302 Found: The resource has been temporarily moved to a different URI.
• 304 Not Modified: The resource has not been modified since the last request.
• 307 Temporary Redirect: The request should be repeated with another URI but future requests should still use the original URI.

4. 4xx (Client Errors):

These codes indicate that the client seems to have made an error.

• 400 Bad Request: The request cannot be processed due to client error.
• 401 Unauthorized: The client must authenticate itself to get the requested response.
• 403 Forbidden: The client does not have access rights to the content.
• 404 Not Found: The server cannot find the requested resource.
• 405 Method Not Allowed: The HTTP method used is not supported for this resource.
• 429 Too Many Requests: The client has sent too many requests in a given amount of time.

5. 5xx (Server Errors):

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

• 500 Internal Server Error: The server encountered a situation it doesn’t know how to handle.
• 501 Not Implemented: The request method is not supported by the server and cannot be handled.
• 502 Bad Gateway: The server, while acting as a gateway or proxy, received an invalid response from an inbound server.
• 503 Service Unavailable: The server cannot handle the request (due to maintenance or overload).
• 504 Gateway Timeout: The gateway or proxy did not receive a timely response from the upstream server.

These are just some of the most common HTTP status codes. There are many more, each serving a specific purpose in the realm of client-server communication.