HTTP Status Codes: Understanding Web Server Responses

Learn about HTTP status codes and what they indicate about web server responses to client requests. This guide explains different status code categories (1xx, 2xx, 3xx, 4xx, 5xx) and provides examples to help you understand and troubleshoot web server communication.

Understanding HTTP Status Codes

Introduction to HTTP Status Codes

HTTP (Hypertext Transfer Protocol) status codes are three-digit codes returned by a web server in response to a client's request (e.g., a web browser requesting a web page). They communicate the outcome of the request, indicating success, failure, redirection, or the need for further action. Understanding these codes is essential for web developers and anyone working with web servers.

Categorization of HTTP Status Codes

Status codes are categorized into five classes based on their first digit:

1xx: Informational

The request was received and is being processed. The client should wait for a further response.

  • 100 Continue: Continue sending the request body.
  • 101 Switching Protocols: Server is switching protocols.
  • 102 Processing: Request accepted; processing in progress.

2xx: Success

The request was successfully received, understood, and accepted.

  • 200 OK: Request successful; data returned.
  • 201 Created: A new resource was created.
  • 202 Accepted: Request accepted; processing not yet complete.
  • 203 Non-Authoritative Information: Response from a proxy server.
  • 204 No Content: Request successful, but no content to return.
  • 205 Reset Content: Client should reset the content.
  • 206 Partial Content: Only part of the requested content was sent.
  • 207 Multi-Status: Multiple status codes returned.
  • 208 Already Reported: Resource already reported.

3xx: Redirection

Further action is required to complete the request, typically involving redirection to a different URL.

  • 301 Moved Permanently: Resource permanently moved.
  • 308 Permanent Redirect: Similar to 301, but preserving the HTTP method.
  • 302 Found: Resource temporarily moved.
  • 303 See Other: Use a GET request to access the resource at a new URL.
  • 307 Temporary Redirect: Similar to 302, preserving the HTTP method.
  • 300 Multiple Choices: Multiple options available.
  • 304 Not Modified: Resource hasn't changed since the last request.

4xx: Client Error

The request contained an error (bad syntax, missing information, unauthorized access).

  • 400 Bad Request: Invalid request syntax.
  • 401 Unauthorized: Requires authentication.
  • 403 Forbidden: Access denied.
  • 404 Not Found: Resource not found on the server.
  • 405 Method Not Allowed: The HTTP method used is not supported.
  • 406 Not Acceptable: The server can't provide the resource in the requested format.

5xx: Server Error

An error occurred on the server, preventing it from fulfilling the request.

  • 500 Internal Server Error: Generic server error.
  • 501 Not Implemented: Server doesn't support the request.
  • 502 Bad Gateway: Problem with a proxy server or other intermediary.
  • 503 Service Unavailable: Server is temporarily unavailable.
  • 504 Gateway Timeout: Timeout waiting for a response from another server.
  • 505 HTTP Version Not Supported: The server doesn't support the requested HTTP version.
  • 507 Insufficient Storage: Server is out of disk space.
  • 510 Not Extended: Requires additional extensions to process the request.

Conclusion

HTTP status codes are crucial for understanding the outcome of web requests. They provide valuable information for developers, allowing for better error handling and improved user experiences.