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Free tool · SSL

Free SSL Checker — with expiry reminders

Check any website’s TLS/SSL certificate in seconds. This free SSL checker reads the live certificate a domain is actually serving — expiry date, days remaining, issuer, Subject Alternative Names, signature algorithm and key strength — and grades it. Then it does what other checkers don’t: it can email you before your certificate expires, so HTTPS never lapses by surprise.

Enter a bare domain (no https:// or path). We check port 443.

How this works

When you run a check, the tool opens a TLS connection to the host on port 443 and reads the certificate the server presents — the same certificate your visitors’ browsers receive. It parses the X.509 certificate to extract the expiry date, issuer, Subject Alternative Names, signature algorithm and key strength, then runs a set of checks (validity window, hostname match, issuer trust, signature and key strength) to produce a grade. If the live handshake can’t complete, it falls back to public Certificate Transparency data and says so. We never store, log, or publish the domains you check.

A free SSL certificate checker that actually reminds you

Almost every SSL outage has the same root cause: a certificate expired and nobody noticed until the site went down. Publicly trusted certificates are now capped at roughly 398 days, and the industry is moving toward even shorter lifetimes — which means more renewals, and more chances for one to slip through. A traditional SSL checker tells you the expiry date; this one tells you, then emails you before it’s too late.

Enter a domain and the tool performs a real TLS handshake, reads the live certificate, and shows you exactly what your visitors’ browsers see: how many days until expiry, who issued it, every hostname it covers via its Subject Alternative Names, the signature algorithm, and the public-key type and size. Each result is graded with a plain-English pass, warning or fail, so you can tell at a glance whether HTTPS is healthy or about to break.

SSL expiry reminders, done properly

After a check, add your email and pick when you want to hear from us — 30, 7 and 1 day before expiry are the defaults, but you can choose anything from 60 days out to the day before. We confirm your address with a single double opt-in email (so nobody can sign you up without consent), then keep an eye on the certificate. If you renew early, we detect the new certificate and quietly re-arm your reminders against the new expiry. Every reminder email carries a one-click unsubscribe, and the only data we keep is the domain, your email, and your schedule.

A privacy-first SSLShopper & SSL.org alternative

If you’ve used SSLShopper or SSL.org to verify a certificate, this covers the same core job — reading the served certificate and checking its validity, issuer, chain and hostname coverage — with two deliberate differences. First, it adds the expiry reminder those tools don’t have, turning a one-off check into ongoing protection. Second, it’s privacy-first: it doesn’t store or publish the domains you look up. It’s a fast, no-friction certificate checker for developers, sysadmins and security teams who want the answer — and a safety net — without handing over their lookup history.

What the SSL checker verifies

Each check reports the validity window (and flags an expired or not-yet-valid certificate), performs a hostname match against the Subject Alternative Names, confirms the certificate is not self-signed, checks the signature algorithm (flagging deprecated SHA-1), and assesses key strength (flagging RSA keys under 2048 bits). It also notes when a certificate’s lifetime exceeds the 398-day maximum. Together these roll up into an A+ to F grade — a quick, honest read on whether a site’s TLS is in good shape.

Need a full TLS & security review?

A certificate check is the surface. If you want your whole TLS configuration, headers and application security assessed, get in touch with our penetration-testing team.

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SSL checker — frequently asked questions

What is an SSL checker?

An SSL checker is an online tool that inspects the TLS/SSL certificate a website is serving and reports its key details — who it was issued to and by, when it expires, which hostnames it covers, the signature algorithm, and the public-key strength. This one connects to the host over TLS, reads the certificate the server is actually presenting, and grades it, so you can confirm HTTPS is configured correctly before your visitors hit a security warning.

How do I check an SSL certificate for a domain?

Enter the domain (for example example.com), complete the quick bot check, and click “Check SSL”. The tool opens a TLS connection to the host on port 443, reads the certificate it serves, and shows the expiry date and days remaining, the issuer, the Subject Alternative Names, the signature algorithm, the key type and size, and a pass/warn/fail breakdown with an overall grade.

Can this tool remind me before my SSL certificate expires?

Yes — that’s the feature most SSL checkers are missing. After a check you can enter your email and choose when to be reminded (for example 30, 7 and 1 day before expiry). We send a confirmation email first (double opt-in), then watch the certificate and email you ahead of expiry. If you renew early we detect the new certificate automatically and re-arm the reminders. Every reminder email has a one-click unsubscribe.

Is this SSL checker free?

Yes. The certificate check and the expiry-reminder service are both completely free, with no account or API key required. The reminder only needs an email address so we can notify you.

Does it read the live certificate or a cached one?

It reads the live certificate. The tool performs a real TLS handshake to the host each time you run a check, so the expiry, issuer and hostname coverage reflect exactly what the server is presenting at that moment — not a cached or previously logged copy. If the live handshake can’t be completed (for example a TLS 1.3-only server that encrypts its certificate, or an unreachable host) it falls back to the most recent Certificate Transparency record and labels the result accordingly.

What does “days until expiry” mean and why does it matter?

It’s the number of days left before the certificate’s notAfter date. Once a certificate expires, browsers show a full-page security warning and most clients refuse to connect, which takes the site (and any APIs behind the same certificate) offline. Because publicly trusted certificates are now capped at around 398 days and many auto-renew on short cycles, an expiry that slips through the cracks is one of the most common causes of avoidable downtime — which is exactly what the reminder feature prevents.

What is a SAN (Subject Alternative Name)?

The Subject Alternative Name extension lists every hostname a certificate is valid for. Modern certificates rely on SANs rather than the legacy Common Name, and a certificate is only trusted for a hostname if that exact name — or a matching wildcard such as *.example.com — appears in the SAN list. The checker shows the full SAN list and flags whether the domain you entered is actually covered.

Does the certificate need to match the hostname?

Yes. For a browser to trust the connection, the hostname being visited must appear in the certificate’s SAN list (or match a wildcard entry). If it doesn’t, browsers raise a “certificate name mismatch” error even when the certificate itself is otherwise valid. This tool performs that hostname-match check for you and marks it as a pass or fail.

What makes a certificate “weak” or untrusted?

Common problems are: an expired or not-yet-valid date range; a self-signed issuer that no browser trusts; a deprecated SHA-1 signature; an RSA key smaller than 2048 bits; or a hostname the certificate doesn’t cover. The grade combines these — any hard failure drops the certificate to an F, while warnings (such as a fast-approaching expiry) lower it from A.

How is this different from SSLShopper or SSL.org?

It does the same core certificate inspection, then adds the thing those tools don’t: a free, double-opt-in expiry-reminder service that emails you before your certificate lapses and re-arms itself when you renew. It reads the live served certificate, gives a clear pass/warn/fail grade with plain-English explanations, never stores or publishes the domains you look up, and is built and maintained by a professional penetration-testing team.

Do you store the domains I check?

No. Certificate checks are processed in real time and returned to your browser only — we don’t store, log, or publish the domains you look up. The only data we retain is what you explicitly give us for a reminder: the domain, your email address, and your chosen reminder schedule, kept solely to send those reminders and removed when you unsubscribe.

Can I check SSL on a non-standard port or an internal host?

This tool checks the standard HTTPS port (443) on publicly reachable hosts. It validates the input as a public domain name and the platform blocks connections to private or internal addresses, so it can’t be pointed at internal infrastructure. For internal certificate management or a full TLS configuration audit, get in touch about a professional assessment.