Problem family
Networking troubleshooting
These records share a system family, but each page stays scoped to one symptom or failure state.
VERIFIED
Cloudflare 403 Forbidden: origin or Cloudflare?Identify who generated the 403 before changing rules: Cloudflare-generated and origin-generated 403 responses require different evidence. Preserve the Ray ID, response headers, URL and timestamp, then compare origin logs or Cloudflare security events. This source-reviewed guide keeps the next step tied to the evidence you can collect safely.
Reviewed Sep 25, 2026Public launch · Cloudflare
VERIFIEDCloudflare Error 1015: you are being rate limitedTreat 1015 as a rate-limit response. Identify the request pattern, affected client identity and configured threshold before increasing limits or disabling a control. Slow or stop the offending pattern first. This source-reviewed guide keeps the next step tied to the evidence you can collect safely.
Reviewed Sep 25, 2026Public launch · Cloudflare
VERIFIEDCloudflare Error 1016: Origin DNS errorVerify the configured origin hostname or CNAME target resolves correctly from the authoritative DNS side. Do not change application code or browser settings: 1016 is an origin-name resolution problem. This source-reviewed guide keeps the next step tied to the evidence you can collect safely.
Reviewed Sep 25, 2026Public launch · Cloudflare
VERIFIEDCloudflare 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.
Reviewed Sep 26, 2026Editorial hold · Cloudflare
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.
Reviewed Sep 8, 2026Editorial hold · Cloudflare
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.
Reviewed Sep 26, 2026Public launch · Cloudflare
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.
Reviewed Sep 26, 2026Public launch · Cloudflare
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.
Reviewed Sep 8, 2026Public launch · Cloudflare
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.
Reviewed Sep 8, 2026Public launch · Cloudflare
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.
Reviewed Sep 26, 2026Public launch · Cloudflare
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.
Reviewed Sep 26, 2026Editorial hold · Cloudflare
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.
Reviewed Sep 26, 2026Editorial hold · Cloudflare
VERIFIEDDNS_PROBE_FINISHED_NO_INTERNET: check connection scope firstDNS_PROBE_FINISHED_NO_INTERNET? Determine whether the connection fails across sites and devices before resetting Chrome, DNS settings or the network stack. This source-reviewed guide keeps the next action tied to the evidence you can collect safely.
Reviewed Sep 26, 2026Public launch · DNS
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.
Reviewed Sep 6, 2026Public launch · DNS