HTTP 523 – Origin Is Unreachable
(Cloudflare) Cloudflare could not reach the origin server, often due to DNS or routing problems.
Common use case
Typically points to a DNS record pointing at a dead IP, an origin server that has been taken offline, or a routing/BGP issue between Cloudflare and the host.
History
A Cloudflare-specific extension.
Did you know?
Unlike 522 (which implies the origin is reachable but slow to respond), 523 means Cloudflare couldn't even find a route to it.