$ errors.fyi/cloudflare/521 128 namespaces · 4,025 codes

cloudflare · cloudflare/521

521

Web Server Is Down

The origin server refused the TCP connection from Cloudflare. The origin may be offline, overloaded, or blocking Cloudflare's IP ranges.

Also defined in

ftp Data Connection Already Open The data connection is already open; a PORT or PASV command cannot be accepted while a data connection is active.
smtp Domain does not accept mail The server does not accept mail for this domain. The connection should be terminated.

In this namespace

← previous 520 Web Server Is Returning an Unknown Error next → 522 Connection Timed Out

520 521 522 523 524 525 526

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