5xx Server errors · Cloudflare (not part of the HTTP standard)
525 SSL Handshake Failed
Cloudflare couldn't complete a TLS handshake with the origin.
Common causes
- The origin has no valid certificate, or doesn't support the TLS settings Cloudflare needs.
- SSL mode set to Full or Full (strict) while the origin only serves HTTP.
How to fix it
- Install a valid certificate on the origin (Cloudflare's free Origin CA works).
- Match Cloudflare's SSL mode to what the origin supports.
Find out the moment your site returns 525
Spot Downtime monitors count this as down and alert you, since visitors see an error. (The public “Is it down?” checker treats 4xx answers from big sites as online, because many refuse automated requests.)