526 Invalid SSL Certificate

The origin presented a certificate Cloudflare could not validate, with the Full (strict) TLS mode on.

Unofficial code. 526 is used only by Cloudflare. It is not in the IANA registry or any HTTP standard, and other software may give the number a different meaning or none.

Code: 526
Reason phrase: Invalid SSL Certificate
Class: 5xx Server error
Used by: Cloudflare
Cacheable by default: No

What it means

Server error: the request may be fine, but the server failed to carry it out.

Usual causes. An expired or self-signed certificate, or one issued for a different host name.

What to do. Renew the certificate or install a Cloudflare Origin CA certificate on the server.

How clients and crawlers treat it

Google Search. Googlebot sees the 5xx code Cloudflare sends and treats it like any server error: it slows down crawling, and URLs that keep failing are eventually dropped from the index. Source: Google Search Central, How HTTP status codes, and network and DNS errors affect Google Search.

Caching. Not cacheable by default (RFC 9110 section 15.1 does not list it). A cache stores it only when the response says so with Cache-Control or Expires.

Example response

HTTP/1.1 526 Invalid SSL Certificate
Content-Type: text/plain; charset=utf-8

Invalid SSL Certificate

Related codes

All status codes · All 5xx codes

Names and numbers from the IANA HTTP Status Code Registry (this code is not in it). Google Search behaviour as documented by Google Search Central.