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HTTP Status Codes

Three-digit codes returned by web servers to indicate the result of an HTTP request.

Web TechnologiesAlso called: "response codes", "http codes"

Status codes communicate success, redirection, client errors, and server errors.

Categories

  • 1xx (Informational): Request received, continuing process.
  • 2xx (Success): Request successfully received and processed (200 OK, 201 Created).
  • 3xx (Redirection): Further action needed (301 Moved, 302 Found, 304 Not Modified).
  • 4xx (Client Error): Bad request from client (400 Bad Request, 401 Unauthorized, 404 Not Found).
  • 5xx (Server Error): Server failed to fulfill request (500 Internal Error, 502 Bad Gateway, 503 Unavailable).

Security relevance

  • 401/403 indicate authentication/authorization issues.
  • 404 can expose information about application structure.
  • Excessive 5xx may indicate DoS or misconfigurations.