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How to Fix SSL Hostname Mismatch Errors

Updated: April 21, 2026 · By Website Checker editorial team

Hostname mismatch means the certificate does not include the exact host requested by the client. Browsers and API clients reject this to prevent man-in-the-middle attacks.

Typical mismatch patterns

  • Certificate includes www.example.com but request is example.com.
  • Certificate issued for staging host but installed on production.
  • Wildcard expected to cover apex (it does not cover the root domain).

Fix checklist

  1. List all hostnames you serve (example.com, www, subdomains).
  2. Issue/reissue certificate with correct SAN entries for each hostname.
  3. Install certificate and full chain on the active edge/proxy node.
  4. Validate HTTPS redirects so traffic lands on covered hostnames only.
  5. Retest with Website Checker and browser.

Wildcard reminder

*.example.com covers subdomains like api.example.com, but not example.com. If you serve both, include both names in SANs.

If mismatch appears intermittently

  • Check load balancer pools for nodes with old certificates.
  • Check CDN edge deployment status in all regions.
  • Verify automation did not renew one cert but deploy another.

If SSL is healthy but you still get downtime codes, continue with 5xx troubleshooting.