Problem family
Networking troubleshooting
These records share a system family, but each page stays scoped to one symptom or failure state.
VERIFIED
Cloudflare 502 Bad Gateway: origin or edge?Cloudflare says 502 and 504 errors most commonly originate at the web server, but Cloudflare can also generate them. The first diagnostic task is identifying whether the origin or Cloudflare produced the response.
Editorial holdCloudflare
VERIFIEDCloudflare Error 520: Web server returned an unknown errorCloudflare 520 is generated when the origin sends an empty, unknown or unexpected response. Common causes include origin crashes, malformed or oversized headers, firewall/security blocks, incorrect HTTP/2-to-origin behavior, or an early connection close. The useful evidence is the affected URL, Ray ID and origin logs.
Editorial holdCloudflare
VERIFIEDCloudflare Error 521: Web server is downCloudflare defines Error 521 as the origin web server refusing connections from Cloudflare. Common causes include an offline origin application or security rules blocking Cloudflare IP ranges.
Public launchCloudflare
VERIFIEDCloudflare Error 522: Connection timed outCloudflare defines Error 522 as a timeout while contacting the origin. It can occur before the TCP connection is established or after connection when the origin does not acknowledge the request in time.
Public launchCloudflare
VERIFIEDCloudflare Error 523: Origin is unreachableCloudflare 523 is a routing/reachability problem: Cloudflare cannot contact the configured origin because the origin IP is wrong or the network path has no usable route. It is distinct from 521 refusal and 522 timeout, so the fastest checks are DNS origin address and routing evidence rather than application code.
Public launchCloudflare
VERIFIEDCloudflare Error 524: A timeout occurredCloudflare 524 means the TCP connection to the origin succeeded, but the origin did not return an HTTP response within the proxy read timeout (125 seconds by default) or did not complete a write in time. That makes slow application work, long database queries and resource saturation more relevant than firewall reachability.
Public launchCloudflare
VERIFIEDCloudflare Error 525: SSL handshake failedCloudflare Error 525 is an origin-side TLS handshake failure while Full or Full (Strict) encryption is in use. Confirm the origin is actually serving HTTPS on the expected port and hostname, then inspect SNI/cipher/certificate configuration instead of changing browser settings.
Public launchNetworking
VERIFIEDCloudflare Error 526: invalid SSL certificateCloudflare Error 526 is a certificate-validation failure at the origin under Full (Strict). Check the origin certificate’s expiry, hostname coverage, chain and trust source, and confirm the origin serves the correct certificate for the requested hostname.
Editorial holdNetworking
VERIFIEDERR_TOO_MANY_REDIRECTS on CloudflareCloudflare says redirect loops commonly come from a conflict between SSL/TLS encryption mode, edge certificate options or redirect rules and the redirects already configured at the origin.
Editorial holdCloudflare
VERIFIEDDNS_PROBE_FINISHED_NXDOMAIN: what it means and what to checkDNS_PROBE_FINISHED_NXDOMAIN means the DNS lookup completed with NXDOMAIN: the resolver determined that the requested name does not exist. For site owners, missing or incorrect DNS records are a primary place to check.
Public launchDNS