← All status codes5xx – Server Error

HTTP 521 – Web Server Is Down

(Cloudflare) The origin server refused the connection from Cloudflare, usually because it is offline.

Other 5xx codes

500Internal Server Error501Not Implemented502Bad Gateway503Service Unavailable504Gateway Timeout505HTTP Version Not Supported507Insufficient Storage508Loop Detected511Network Authentication Required520Web Server Returned An Unknown Error522Connection Timed Out523Origin Is Unreachable524A Timeout Occurred525SSL Handshake Failed526Invalid SSL Certificate527Railgun Error530Origin DNS Error540Temporarily Disabled561Unauthorized598Network Read Timeout Error599Network Connect Timeout Error