SSL Certificate Errors: Expired, Invalid and Mixed-Content Fixes

Why browsers block HTTPS sites — expired certificates, hostname mismatch, incomplete chains — and how to diagnose and fix each SSL error.

The 4 common causes

Expired cert (most common on small sites). Hostname mismatch (cert for www, request bare). Incomplete chain (missing intermediate). Device clock wrong (your laptop says 2019).

What to do as a visitor

Check the date on your device, try another network, never bypass the warning on login/payment pages. Our checker flags TLS separately from offline.

What to do as an owner

Automate renewal (ACME/Let's Encrypt), serve the full chain, enable HSTS after HTTPS is stable, monitor expiry with alerts.

Test it now: run a live check → then re-read your result with this guide. Each check + guide read is another pageview that funds the free tool.

FAQ

Is an SSL error the same as down?

No — the network path works, identity verification failed. Browsers block it, but the server is reachable.

Why “not private” on office Wi-Fi?

Captive portals / TLS inspection proxies. Finish the portal login or use mobile data to confirm.