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Error 523: Origin Is Unreachable (Cloudflare)

Updated Free mock REST & WebSocket APIs

Error 523 Origin Is Unreachable — Cloudflare couldn't reach the origin at all — usually a DNS or routing problem.

Class
5xx Server Error
Defined in
Unofficial (Cloudflare)
Official
No — Cloudflare-specific
Cacheable by default
No (unless Cache-Control/Expires say so)
Safe to retry
Yes, after a delay (respect Retry-After)

Try it: get a real 523 response

Our test endpoint answers every request with 523 Origin Is Unreachable.

curl -i https://mockfox.dev/api/status/523

Use it in tests, health-check monitors or to see how your client handles a 523. Add ?delay=2000 to slow it down.

What does error 523 mean?

Error 523 "Origin is unreachable" is a Cloudflare status meaning Cloudflare can't find a route to the origin server's IP address at all — typically because the IP in the DNS record is wrong or the origin network is down.

When is 523 used?

  • The DNS record points to an IP that no longer exists (old server, changed hosting).
  • A private or reserved IP (10.x, 192.168.x) was entered as the origin.
  • The hosting provider's network or BGP routes are down.

Common causes of error 523

  • Incorrect A/AAAA record in Cloudflare DNS.
  • Hosting provider outage or the server was deleted.
  • IPv6 AAAA record pointing to an address the origin doesn't actually serve.

How to fix 523 Origin Is Unreachable

If you're visiting the site

  1. Nothing to do but wait — the website's server can't be reached by Cloudflare.

If you run the site or API (developers)

  1. Check the DNS records in the Cloudflare dashboard against your host's current IP.
  2. Remove stale AAAA records if the origin doesn't support IPv6.
  3. Ask your host whether their network is having routing issues; traceroute to the origin from several locations.

Returning or handling 523: server examples

Check routing

traceroute 203.0.113.10
mtr -rwc 50 203.0.113.10

Example 523 response

HTTP/2 523
server: cloudflare
cf-ray: 8d2f1a3b4c5d6e7f-SJC
content-type: text/html; charset=UTF-8

Related status codes

Related tools

Frequently asked questions

What causes error 523?

Cloudflare has no network route to the origin IP — usually a wrong DNS record, a decommissioned server or a hosting network outage.

523 vs 522?

522: the origin is reachable but didn't answer in time. 523: the origin's address can't be reached at all.

How fast does fixing the DNS record work?

Changes to proxied records in Cloudflare take effect within seconds to a few minutes, because Cloudflare itself uses the new origin IP.