What do you understand by the HTTP Status Codes ?

The HTTP or the HyperText Transfer Protocol is a protocol of the application layer. It helps in establishing communication between a web browser and a web server. When a client requests any information, the browser sends a response using numeric status codes. These status codes are in the form of 3-digit numbers ranging from 100 - 599. The client then acts on the response accordingly. The client may not always fully understand the status code or the response but may understand the nature/class of the response by seeing the leftmost/first digit of the numeric status code.

The HTTP status codes can be categorized into five standard classes using their first digit:

• 1xx - This stands for an informational response, that is, the request was received, continuing process, and should wait for the final response.
• 2xx - This stands for a successful response, that is,  the request was successfully received, understood, and accepted.
• 3xx - This stands for redirection response, that is, some further action needs to be taken in order to complete the request.
• 4xx - This stands for client error, that is, the request contains bad syntax or cannot be fulfilled.
• 5xx - This stands for server error, that is, the server failed to fulfill an apparently valid request.

The other two digits have no such significant role when defining the classes.

A few examples of each class of status code have been mentioned below:

• 101 - Switching Protocols - It means the server has been asked to switch protocols and the server has agreed to do so.
• 102 - Processing - It means that the request may contain many sub-requests like file operations, which may take a long time to complete. This helps in preventing the client from assuming that the request has timed out.
• 200 - OK - This is a standard response to all the successful HTTP requests.
• 202 - Accepted - This means that the request has been accepted by the server and is not completed yet.
• 307 - Temporary Redirect - This means that the current request that is being sent to the server should be repeated with another URL. The future requests would still be sent to the original URL.
• 308 - Permanent Redirect - Unlike the previous one, here the current and all the future requests will be redirected to another given URL.
• 404 - Not Found - This means simply that the request been sent has not been found but it might be available in the future.
• 424 - Failed Dependency - It means the request failed because it depended on another request and that request also failed.
• 500 - Internal Server Error - A standard error message when some unexpected situation occurs and the server doesn't exactly know what it is.
• 504 - Gateway Timeout - This means that the server did not receive a response in time.