How do I check an SSL certificate?

Enter a website hostname in the SSL checker and submit it. Webalert connects to the HTTPS service from outside your network and reports whether the certificate is trusted, its issuer, validity period, expiry countdown, and TLS version.

How can I tell when an SSL certificate expires?

Run the website through the SSL checker. The result shows the certificate's exact valid-to date and the number of days remaining. Set up SSL monitoring before the countdown reaches zero so renewal problems do not become an outage.

What does an invalid SSL certificate mean?

An invalid certificate may be expired, issued for a different hostname, self-signed, or served with an incomplete trust chain. Browsers can warn or block visitors until the certificate or server configuration is corrected.

Can I monitor SSL certificate expiry automatically?

Yes. Webalert can check your HTTPS endpoint on a schedule and alert you before the certificate expires or becomes invalid. Start free with no credit card required.

SSL Certificate Checker

Check an HTTPS certificate's expiry, issuer, validity period, and TLS details from outside your network. Free, instant, and no sign-up required.

Running this website? Get alerted before your certificate expires — free forever, no credit card.

What this SSL checker verifies

A certificate can be present but still unusable to visitors. This external check connects to the hostname over TLS and verifies the certificate chain your public users receive.

Expiry countdown

See the exact valid-to date and days remaining, so renewals are planned before they become incidents.

Issuer and subject

Confirm which certificate authority issued the certificate and which hostname it identifies.

Validity period

Check when the certificate became valid and whether it is currently expired or trusted.

TLS connection

Inspect the negotiated TLS version from an independent server-side connection.

Why SSL certificates cause outages

Browsers and API clients reject an expired, mismatched, or untrusted certificate before they can load your application. A site can be healthy at the HTTP layer and still appear down because its TLS handshake fails.

Use the checker for a fast one-off diagnosis. For a site you operate, pair it with automated SSL monitoring so renewal failures are caught before visitors see a certificate warning. If the certificate is only one symptom, confirm the rest of the endpoint with the website down checker.

Frequently asked questions

How do I check an SSL certificate?: Enter a hostname above. We connect from Webalert infrastructure and report trust, issuer, validity dates, expiry countdown, and TLS version.
How can I tell when an SSL certificate expires?: The result includes the exact expiry date and days remaining. Monitor the certificate automatically before the countdown reaches zero.
What does an invalid SSL certificate mean?: It may be expired, issued for another hostname, self-signed, or served with an incomplete trust chain. Browsers may warn or block visitors.
Can I monitor SSL certificate expiry automatically?: Yes. Webalert SSL monitoring checks your endpoint on a schedule and alerts you before expiry or invalidation.