HTTP Requests and Responses Explained

HTTP (Hypertext Transfer Protocol) is the foundational protocol used for transferring data over the web. It allows web browsers and servers to communicate by sending requests and receiving responses. The responses from the server are accompanied by status codes that indicate the result of the request. Below is an overview of HTTP requests and a detailed description of common HTTP response status codes.

HTTP requests are made by a client to request an action on a resource identified by a URI (Uniform Resource Identifier). There are several types of HTTP requests, each designed for specific actions:

• GET: Requests data from a specified resource.
• POST: Submits data to be processed to a specified resource.
• PUT: Updates a specified resource with the data provided.
• DELETE: Deletes a specified resource.
• HEAD: Similar to GET, but it requests only the headers and status line, not the body of the response.
• PATCH: Applies partial modifications to a resource.
• OPTIONS: Returns the HTTP methods that the server supports for a specific URL.

HTTP response status codes are issued by a server in response to a client's request made to the server. These codes are divided into five categories:

1xx: Informational

• 100 Continue: The server has received the request headers, and the client should proceed to send the request body.

2xx: Success

• 200 OK: The request has succeeded. The information returned with the response depends on the method used in the request.
• 201 Created: The request has been fulfilled, leading to the creation of a new resource.
• 202 Accepted: The request has been accepted for processing, but the processing has not been completed.
• 204 No Content: The server successfully processed the request but is not returning any content.

3xx: Redirection

• 301 Moved Permanently: The URL of the requested resource has been changed permanently. The new URL is given in the response.
• 302 Found: Indicates that the resource is temporarily under a different URI.
• 304 Not Modified: Indicates that the resource has not been modified since the last request.

4xx: Client Error

• 400 Bad Request: The server cannot or will not process the request due to an apparent client error (e.g., malformed request syntax).
• 401 Unauthorized: Authentication is required and has failed or has not yet been provided.
• 403 Forbidden: The server understood the request but refuses to authorize it.
• 404 Not Found: The requested resource could not be found but may be available in the future.
• 405 Method Not Allowed: A request method is not supported for the requested resource.

5xx: Server Error

• 500 Internal Server Error: A generic error message, given when an unexpected condition was encountered and no more specific message is suitable.
• 501 Not Implemented: The server either does not recognize the request method, or it lacks the ability to fulfill the request.
• 503 Service Unavailable: The server is currently unavailable (because it is overloaded or down for maintenance).

Each of these status codes provides valuable information about the outcome of an HTTP request. Understanding these codes is crucial for developers working on web applications, as it helps in debugging and improving the reliability and usability of web services.