How long are SSL certificates valid?

Public certificates now last up to ~398 days; free ones like Let's Encrypt last 90 days and are meant to auto-renew.

What does “hostname mismatch” mean?

The certificate doesn't list the exact name visitors use, so the browser can't trust it for that name. Reissue with the right SANs.

Is a self-signed certificate okay?

Only for internal testing. Public visitors will see warnings — use a trusted CA in production.

How to check an SSL certificate

How to check a website's SSL certificate

An SSL/TLS certificate is what puts the padlock in the address bar. If it expires or is misconfigured, browsers warn visitors and some simply can't reach your site.

Tool: SSL/TLS checker Try it now — free, no signup. Open →

What it is

An SSL/TLS certificate proves your domain's identity and encrypts traffic between the browser and your server. It has an issuer (the certificate authority), a validity window, the hostnames it covers (the SAN list), and a chain back to a trusted root.

Why it matters

If a certificate expires, doesn't match the hostname, or ships an incomplete chain, browsers show a full-page security warning. That kills trust, conversions and SEO — and on strict clients the site won't load at all.

How to check

Enter your domain in the tool above. It shows days until expiry, the issuer, the protocol version, the SAN/wildcard coverage, whether the hostname matches, and whether HSTS is enabled.

How to fix

Expiring soon? Renew now — and automate renewal (Let's Encrypt / your host) so it never lapses.
Hostname mismatch? Reissue the certificate with the correct SAN entries (e.g. both example.com and www.example.com).
Chain incomplete? Install the intermediate certificate alongside the leaf.
Enable HSTS to force HTTPS.