SSL Certificate Checker

SSL Certificate Checker: what it is for

Enter a site and see whether it opens over HTTPS, how many days until the SSL certificate expires on a colored gauge, who issued it (Let's Encrypt, Google Trust Services, Sectigo, DigiCert and others), the validity period, the domains covered and whether the site uses HSTS. The history shows the latest certificates issued for the domain on a timeline, based on the public Certificate Transparency logs.

Useful to keep the certificate from expiring and the site from showing as not secure.

How to use

1. Enter the site address.
2. Tap Check SSL.
3. See the days left, the issuer and the history.

When to use it

• Check when your site's SSL expires.
• Confirm automatic renewal worked.
• See which subdomains the certificate covers.

Frequently asked questions

What is an SSL certificate?

It is the file that lets a site use HTTPS: it encrypts data between your browser and the server and proves the site really belongs to that domain. Without it, the browser shows a not secure warning.

What happens when SSL expires?

The browser starts blocking the site with an insecure connection warning, and most visitors give up. So renew ahead of time: ideally use automatic renewal and check when fewer than 30 days are left.

Where does the certificate data come from?

The tool tests whether the site opens over HTTPS and fetches the certificates issued for the domain from the public Certificate Transparency logs, where every authority must publish the certificates it issues.

What is HSTS?

A header that tells the browser to always open the site over HTTPS, even if someone types http://. It protects against attacks that try to downgrade the connection to HTTP.

Is it really free?

Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 are free.

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