What it means
In Full (strict) mode, Cloudflare requires the origin to have a valid certificate: not expired, issued by a trusted authority (or Cloudflare Origin CA) and matching the domain name. If it doesn't, a 526 is shown.
Most common causes
- The certificate on the origin has expired.
- A self-signed certificate in Full (strict) mode.
- The certificate doesn't cover the domain or subdomain.
- A missing intermediate certificate chain.
What you can do as a visitor
- You can't fix this error. Try again later.
What the site owner or developer should do
- Renew or install a valid certificate (Let's Encrypt or Cloudflare Origin CA).
- Check that the certificate covers every subdomain you use.
- Install the full certificate chain.
- Set up automatic certificate renewal.
Impact on SEO and Google
As with other Cloudflare 5xx errors: the site is unreachable while the error lasts.
Frequently asked questions
Can I use Cloudflare Origin CA?
Yes. It's free and Cloudflare accepts it in Full (strict) mode.
Why did a 526 appear suddenly?
Most often the certificate on the origin has expired.