Enter a domain to inspect its SSL certificate.
Performs a live TLS handshake — accurate, real-time certificate data.
About the SSL Checker
Inspect the TLS certificate a domain actually serves. The check performs a live handshake and reports the expiry date and days remaining, the issuing authority, every Subject Alternative Name covered, and the full chain. An expired or misconfigured certificate produces a browser warning that stops visitors at the door, so catching it early matters.
How to use the SSL Checker
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Enter the domain
Type the hostname you want to check. The tool connects to it and reads the certificate presented during the handshake.
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Review expiry and issuer
Check how many days remain before expiry and which certificate authority issued the certificate.
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Check the SANs and chain
Confirm the hostname you use is listed in the Subject Alternative Names, and that intermediate certificates are present so the chain validates.
When to use it
Preventing an expiry outage
Check remaining validity before a certificate lapses and starts showing security warnings to every visitor.
Debugging a chain error
Find out whether a certificate fails in some clients because an intermediate certificate is missing from the served chain.
Verifying subdomain coverage
Confirm a certificate actually covers the hostname in use, including www and any additional subdomains.
Frequently asked questions
What does "certificate expired" mean for visitors?
Browsers show a full-page security warning that most users will not click through. In practice an expired certificate takes the site down.
Why does my certificate work in one browser but not another?
Usually a missing intermediate certificate. Some clients cache intermediates from previous connections and succeed, while a fresh client without that cache fails. Serving the complete chain fixes it.
What is a SAN?
A Subject Alternative Name lists the hostnames a certificate is valid for. Modern browsers ignore the legacy Common Name field entirely, so a hostname missing from the SAN list will be rejected.
Does a valid certificate mean the site is safe?
No. It confirms the connection is encrypted and the hostname matches the certificate. It says nothing about the trustworthiness of the operator — phishing sites routinely use valid certificates.
How often should certificates be renewed?
Most public certificates are now issued for 90 days or less and are expected to be renewed automatically. Manual renewal is the main cause of expiry outages.
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