EC
523
HTTPERRORCommon5xx Server Error (Cloudflare)HIGH confidence

Origin Is Unreachable

Production Risk

Critical — entire site is down. Usually caused by infrastructure changes without updating Cloudflare configuration.

What this means

523 Origin Is Unreachable is a Cloudflare-specific error indicating that Cloudflare cannot reach the origin server at the network level — the origin is not reachable via DNS, IP routing, or TCP. Unlike 522 (TCP timeout), 523 means the route to the origin does not exist.

Why it happens
  1. 1The origin server's IP has changed but DNS is not updated.
  2. 2The origin server is offline or has been deprovisioned.
  3. 3A network routing issue makes the origin unreachable from Cloudflare's network.
  4. 4The DNS A record for the origin is deleted or points to a non-existent IP.
How to reproduce

The origin server's cloud instance was terminated without updating the DNS record in Cloudflare.

trigger — this will error
trigger — this will error
# Cloudflare resolves origin IP → no route to host
# EHOSTUNREACH or ENETUNREACH

expected output

HTTP/1.1 523 Origin Is Unreachable

Fix

Update the origin DNS record in Cloudflare

WHEN The origin IP has changed.

Update the origin DNS record in Cloudflare
# In Cloudflare dashboard: DNS → update A record to new origin IP
# or via API:
curl -X PUT 'https://api.cloudflare.com/client/v4/zones/{zone_id}/dns_records/{record_id}' \
  -H 'Authorization: Bearer TOKEN' \
  -d '{"type":"A","name":"origin","content":"new.ip.address"}'

Why this works

Points Cloudflare to the correct origin IP address.

Version notes
Cloudflare

Cloudflare-specific. 523 = no network path to origin; 522 = network path exists but TCP times out.

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