523 Origin Is Unreachable

Cloudflare: it cannot reach the origin at all (routing or DNS problem).

523 at a glance

Code: 523
Name: Origin Is Unreachable
Class: 5xx Server error
Status: Non-standard used by Cloudflare
Documented by: Cloudflare
Cacheable by default: No by default. Caches only store responses with unrecognised status codes if explicit freshness (Cache-Control max-age) is given.

What 523 means

Cloudflare returns 523 when the origin cannot be reached, typically because the origin IP is not routable from Cloudflare: a wrong DNS record, a changed server IP, or a network-level routing failure.

What typically causes a 523

Origin IP changed (new server, dynamic IP) without updating the DNS record in Cloudflare.
AAAA record pointing at an IPv6 address the origin does not actually serve.
Upstream network outage or BGP problem at the host.

Fix it on the server

Verify the DNS records in the Cloudflare dashboard and test the origin IP directly from outside your network.

Fix it as a client or visitor

Retry later.

Headers that go with 523

Header	Role
`CF-RAY`	Request ID for troubleshooting.

Example response

HTTP/1.1 523
Server: cloudflare
Content-Type: text/html