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Status Codes and Their Meanings in HTTP Responses

HTTP response status codes are used to indicate the outcome of specific HTTP requests. These codes fall into five categories: informational responses, successful responses, redirection responses, client error responses, and server error responses.

Status Messages and Their Importance

The accompanying status message is not crucial for clients; they mainly rely on the numeric status code. The message serves as a recommendation, and clients are not obligated to examine it. The message may vary across HTTP versions and RFC documents, and HTTP/2 may not contain a status message at all.

Informational Responses

These responses signify that the request was received and understood but are provisional, prompting the client to wait for a final response. These are typically not visible when using

Successful Responses

These status codes indicate that the server successfully processed the request. Examples include:

  • 200 OK: The server processed the request successfully, typically providing the requested page.
  • 204 No Content: The server responded with valid header information only, useful for more efficient server responses without refreshing pages.

Redirection Responses

These codes imply further action is needed to fulfill the request and are often used for redirection. Examples include:

  • 301 Moved Permanently: The requested page has permanently moved to a new location.
  • 302 Found: The server temporarily responds from a different location but advises future requests to use the original location.
  • 304 Not Modified: The requested page hasn't changed since the last request.
  • 307 Temporary Redirect: Similar to 302, it redirects temporarily.
  • 308 Permanent Redirect: Redirects permanently.

Client Error Responses

These codes indicate an error in the client's request, preventing server processing. Examples include:

  • 400 Bad Request: Server didn't understand the request's syntax.
  • 401 Unauthorized: Authentication is required for access.
  • 403 Forbidden: The server refuses the request.
  • 404 Not Found: The requested page doesn't exist.
  • 408 Request Timeout: The request took too long.
  • 410 Gone: The resource has been permanently removed.
  • 429 Too Many Requests: Client sent too many requests in a short time.

Server Error Responses

These codes indicate server awareness of errors or incapacity to perform the request. Examples include:

  • 500 Internal Server Error: Server encountered unexpected issues.
  • 502 Bad Gateway: Invalid response from another server.
  • 503 Service Unavailable: Server temporarily unavailable
  • 504 Gateway Timeout Error: No timely response from another server, often due to communication delays.