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SSL Checker

Check the HTTPS certificate of any site: expiration, issuer, covered names and chain.

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What this tool does

The SSL checker connects to the site on port 443, just like a browser would, and shows the certificate it presents: who issued it, which names it covers, when it expires, whether the chain is trusted and which TLS version was negotiated. It's the fastest way to find out why the browser says "connection not secure" or to confirm that automatic renewal worked.

How to read the result

  • Status: "valid" when the certificate is trusted, covers the domain and hasn't expired.
  • Issuer: the certificate authority, such as Let's Encrypt, Sectigo or DigiCert.
  • Valid until: the expiration date. Let's Encrypt certificates last 90 days and renew automatically around the last 30 days.
  • Names covered: the domains included in the certificate. If the name you typed isn't listed, the browser shows an error.
  • Chain: the site's certificate and the intermediates up to the root authority. An incomplete chain makes the site fail on some devices.
  • Protocol: TLS 1.2 or 1.3. Older versions are insecure and rejected by browsers.

Common problems

Expired certificate. Automatic renewal failed. On servers with certbot, run the renewal and make sure the web server was reloaded afterward.

Name mismatch. The certificate was issued for another domain. This happens when www wasn't included or when the site is on shared hosting without its own certificate.

Untrusted issuer. The certificate is self-signed or an intermediate is missing from the configuration. Install the full chain (the fullchain file).

Could not connect. Port 443 is closed, blocked by a firewall, or the domain doesn't point to a server with HTTPS.

Frequently asked questions

What is an SSL certificate?

It is a file installed on the server that proves the site's identity and enables an encrypted HTTPS connection. The protocol in use today is TLS, but the name SSL stuck.

How do I know when my certificate expires?

Enter the domain in this tool and look at the Valid until field. We also show how many days are left.

Why does the browser say the site is not secure?

Usually the certificate has expired, doesn't cover the name you visited or wasn't issued by a trusted authority. The result on this page shows which of the three it is.

Is Let's Encrypt trustworthy?

Yes. It is a free certificate authority recognized by every current browser. Certificates last 90 days and renew automatically.

Does the tool test ports other than 443?

No. The check runs only on port 443, the HTTPS default.