523: Origin Is Unreachable, what it means and what to do
This code is not part of the official HTTP standard. It comes from Cloudflare, the network that sits in front of a large share of the web, and you only see it on sites that use Cloudflare. Error 523 means Cloudflare cannot even find a route to the origin server. In Cloudflare's diagnosis this is fundamentally a DNS problem: the DNS record for the site points at an IP address that does not exist, cannot be routed to, or is not the server anymore. The web server might be perfectly healthy at a different address, which is what makes 523 so distinctive: it is an addressing failure, not a server failure.
If you are just visiting a site
- Wait and retry in a few minutes. The problem sits between Cloudflare and the site's own server, and it often clears when that server recovers.
- There is nothing to fix on your device. A different browser, a cleared cache, or a restarted phone produces the same error, because your request reached Cloudflare successfully and failed after that.
- Tell the site owner through another channel if it persists, their social account or a status page. Owners often learn about origin failures from visitors first.
If it is your site behind Cloudflare
- Open your Cloudflare DNS settings and verify the A and AAAA records. The address there must be your origin's current public IP. A server migration or an IP change at the host that never made it into Cloudflare is the number one cause of 523.
- Check for stale or conflicting records. An old AAAA record pointing at a retired IPv6 address can produce 523s for a share of traffic while the IPv4 path works fine, which looks maddeningly intermittent.
- Confirm the origin exists at that address. If the host reassigned or released the server, the record points into the void. Your hosting panel shows the address the server actually has now.
- Allow for propagation after changes. If you just corrected the record, a short window of mixed answers is normal while caches expire.
Visitors: the site's address on file leads nowhere, and only the owner can correct it. Owners: start in the DNS tab, not the server, 523 is an address problem wearing a server error's clothes.
Common questions
What is the difference between 523 and 522? A 522 means Cloudflare knows where the origin should be but the connection timed out. A 523 means Cloudflare cannot reach the origin at all, typically because DNS points to an address that is unroutable or nonexistent. Addressing versus answering.
Why did a 523 appear right after I changed hosting? Because the site's DNS record in Cloudflare still holds the old server's address, or a stale record survived the move. Migrations change the server immediately and the DNS only when someone edits it, and 523 is what that gap looks like.
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