Server errorsNon-standard, Cloudflare
521Web Server Is Down
A content network could not open a connection to your origin server at all.
Browse all HTTP status codesWhen you see it
The origin refused the connection outright. Usually the web server process is stopped, or a firewall is blocking the content network from reaching it.
This is one of the more actionable vendor codes, because it points at exactly two things: is the server running, and is it reachable.
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Status codes
69 of 69 codes. Click a row to copy it.
1xx Informational (4)
2xx Success (10)
3xx Redirection (8)
4xx Client errors (31)
5xx Server errors (16)