526 Invalid SSL Certificate

Unofficial · Cloudflare

Cloudflare could not verify the certificate of the origin server.

What to do

Cloudflare is set to Full (strict), and the origin's certificate did not validate. Check it has not expired, is from a trusted CA or Cloudflare's Origin CA, and names the hostname.

Class
5xx Server Error. The server failed to fulfill a request that looked valid.
Registered
No. Cloudflare sends it, and it is not in the IANA registry, so other servers may mean something else by it.
References
Cloudflare

Every 5xx code

All HTTP status codes, in one table