5xx Server error Non-standard · used by Cloudflare
HTTP 523 Origin Is Unreachable
A Cloudflare code: Cloudflare can’t reach the origin server, typically because the DNS record points at an address that doesn’t route anywhere, or there is a network problem on the way.
Documented in Cloudflare: 5xx errors(opens in a new tab)
//_01 Uptime checks
Is 523 up or down for a monitor?
Uptimecheck HTTP monitor
Default settings
Down. It is outside the default 200–399 range, so a monitor reports an outage once a second check confirms it. If 523 is the answer you expect from that URL, add it to the monitor’s expected status codes.
Is it down? checker
Free, at /is-it-down/
Down. A 5xx means the server, or something in front of it, failed to answer.
//_02 Causes and fixes
Why you see 523 and what to do
Typical causes
- The origin’s IP address changed and the DNS record in Cloudflare wasn’t updated.
- Routing problems at the origin’s hosting provider.
If you run the site
- Check the A and AAAA records in Cloudflare against the server’s real addresses.
If you’re a visitor
- Try again later.
Know the moment your site stops answering as it should
An Uptimecheck monitor requests your page as often as every minute, checks the status code against the ones you expect, confirms a failure with a second check and then alerts you.
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Questions
What does HTTP 523 mean?
A Cloudflare code: Cloudflare can’t reach the origin server, typically because the DNS record points at an address that doesn’t route anywhere, or there is a network problem on the way.
Does an uptime monitor count 523 as down?
Down. It is outside the default 200–399 range, so a monitor reports an outage once a second check confirms it. If 523 is the answer you expect from that URL, add it to the monitor’s expected status codes.
Downtime is obsolete.
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