SSL Certificate Checker

Check any website's SSL/TLS certificate in seconds. Enter a domain and see when the certificate expires, how many days remain, who issued it, whether it is valid right now, and every hostname it covers (the SAN list). To check a non-standard port, add it to the host, for example mail.example.com:993.

How to use it

  1. Type a domain into the field above (for example kwinside.com). You can paste a full URL — the scheme and path are stripped automatically.
  2. Optionally append a port, such as example.com:8443. The default is the HTTPS port 443.
  3. Press Check certificate. The certificate is fetched live from the host over TLS.
  4. Read the result: the highlighted badge tells you at a glance whether the certificate is valid and how many days remain; the table lists the issuer, validity window, SAN and more.

Why use it

Expired SSL certificates break HTTPS, trigger scary browser warnings and can take a site offline for visitors and customers. This checker lets you confirm a certificate's expiry date, verify it was issued by the authority you expect, and see exactly which hostnames it secures via the Subject Alternative Names — so you can catch renewals before they lapse and spot misconfigured or mismatched certificates early.

Frequently asked questions

Is this SSL checker free?
Yes. The SSL certificate checker is free to use with no login and no credit card. Enter any public domain and see its certificate details instantly.
What does the SSL checker show?
It shows the certificate subject (common name), the issuer organization and CN, the validity window (valid-from and valid-to dates), days remaining until expiry, whether the certificate is currently valid, the Subject Alternative Names (SAN) it covers, the serial number and the signature type.
Can I check a certificate on a non-standard port?
Yes. Append the port to the host, for example mail.example.com:993. If you do not specify a port, the checker connects to the default HTTPS port 443.
Why does my certificate show as not valid?
A certificate is reported as not valid when the current time is outside its validity window — either it has expired (valid-to date in the past) or it is not yet active (valid-from date in the future). Check the days-remaining value and renew before it reaches zero.

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