5xx Server errors · Cloudflare (not part of the HTTP standard)
523 Origin Is Unreachable
Cloudflare can't reach the origin at all.
Common causes
- Wrong DNS record pointing Cloudflare to the origin.
- Routing problems to the origin's network.
How to fix it
- Check the A/AAAA/CNAME record in Cloudflare points to the right server.
Find out the moment your site returns 523
Spot Downtime monitors count this as down and alert you, since visitors see an error. (The public “Is it down?” checker treats 4xx answers from big sites as online, because many refuse automated requests.)