What this checker tells you
Every HTTPS site presents a certificate that proves it owns the domain. The checker opens a real TLS connection to port 443, reads what the server sends back, and reports the expiry date, who issued it, the negotiated TLS version and cipher suite, the key type, and whether browsers will trust the chain.
The most common outage cause is a certificate nobody renewed. Check the days remaining before every launch, and again a fortnight out from expiry.
Frequently asked questions
- My certificate is valid but shows a warning.
- The intermediate certificate is probably missing. Install the full chain file your certificate authority supplied, not just the leaf.
- How often should certificates renew?
- Public certificates last 90 days to a year. Automate renewal so it never depends on someone remembering.
- The check says no certificate was returned.
- The site may not serve HTTPS on port 443, or a firewall is blocking the connection. Confirm the host resolves with the DNS lookup tool first.
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