404 Checker
HTTP Status Codes
11 Codes Documented
5XX — Server Error
The server is aware that an internal error occurred or that it is temporarily incapable of completing the request.
HTTP
500
Internal Server Error
RFC 9110
The server encountered an unexpected condition that prevented it from fulfilling the request. This is the generic catch-all status code when an unexpected server error or unhandled backend exception occurs.
HTTP
501
Not Implemented
RFC 9110
The server does not support the functionality required to fulfill the request. Appropriate when the server does not recognize the request method and cannot support it for any resource.
HTTP
502
Bad Gateway
RFC 9110
The server, while acting as a gateway or proxy, received an invalid response from an upstream server it accessed in attempting to fulfill the request. Very common when reverse proxies like Nginx receive an empty or corrupted response from backend applications.
HTTP
503
Service Unavailable
RFC 9110
The server is currently unable to handle the request due to a temporary overload or scheduled maintenance. Commonly accompanied by a Retry-After header. Search engines recognize 503 as a temporary interruption without harming SEO rankings.
HTTP
504
Gateway Timeout
RFC 9110
The server, while acting as a gateway or proxy, did not receive a timely response from an upstream server (such as an origin application server or database) that it needed to access to complete the request.
HTTP
505
HTTP Version Not Supported
RFC 9110
The server does not support, or refuses to support, the major HTTP protocol version that was used in the request message.
HTTP
506
Variant Also Negotiates
RFC 2295
Transparent content negotiation for the request results in a circular reference, indicating an internal server configuration error.
HTTP
507
Insufficient Storage
RFC 4918
The method could not be performed on the resource because the server is unable to store the representation needed to complete the request (WebDAV).
HTTP
508
Loop Detected
RFC 5842
The server terminated an operation because it encountered an infinite loop while processing a request with Depth: infinity (WebDAV).
HTTP
510
Not Extended
RFC 2774
Further extensions to the request are required for the server to fulfill it.
HTTP
511
Network Authentication Required
RFC 6585
The client needs to authenticate to gain network access. Primarily used by Wi-Fi captive portals (such as hotel, airport, or cafe hotspot login screens) before authorizing internet connectivity.
Verify Status Codes in Real-Time
Encountered an unexpected HTTP response on your website? Use our free tool to inspect the full header and status chain.
Launch 404 Checker