SSL Certificate Checker - Expiry, Trust, and Chain

When a browser connects to an HTTPS site, the server hands over a certificate during the TLS handshake — a signed document that says “this is genuinely example.com, and here is the key to encrypt with.” This tool does the same handshake from our server, reads that certificate, and lays out what it contains. The one question almost everyone arrives with is when does it expire, so that is the headline: the tool computes the exact days remaining, and if the date has already passed, how many days ago it lapsed. An expired certificate is the single most common way a working site suddenly greets every visitor with a full-page security warning.

Expiry is only half of trust, though. A browser accepts a certificate only if three things hold at once: it is within its valid dates, its chain links back to a trusted root authority, and it was issued for the hostname you are actually visiting. The tool checks all three and shows a single trusted-or-not verdict, but when the answer is “not trusted” it tells you which condition failed — because an expired certificate, a name mismatch, and a broken chain are three different problems with three different fixes.

Because the check runs from our server rather than your browser, it shows the certificate as the outside internet sees it. That matters for one failure mode in particular: a missing intermediate certificate can look fine in your own browser, which may have cached that intermediate from another site, while failing for a first-time visitor whose browser has not. An external check does not have your cache, so it catches the problem your own browser hides.

This is a certificate inspector, not a full TLS security audit. It reports what the certificate says and whether it validates, but it does not grade your cipher suites, test for protocol downgrade attacks, check revocation status through OCSP, or score the server the way a dedicated lab-style scanner does. It also only speaks to port 443; certificates protecting mail servers, databases, or custom services on other ports are outside its scope, and for those a command-line tool that lets you name the port is the right instrument. Treat a green result here as “the certificate itself is in good shape,” not as a complete clean bill of health for the server's encryption.

As with the other network tools here, the checker refuses private, loopback, and internal addresses, so it cannot be pointed at a machine inside a network it should not reach. It reads public certificate data only, never modifies anything on the target, and does not store the certificates it inspects. Use it to keep an eye on your own domains' expiry dates and to diagnose the trust warnings your visitors report — the two things it is genuinely good at.