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Centoculus

Free tool

SSL checker: is your certificate valid, and when does it expire?

Enter a domain. We connect on port 443 from Europe, read the certificate the server sends and tell you in plain words whether visitors get a secure connection and how many days are left.

What these results mean

Days left
How long the certificate stays valid. When it reaches zero, browsers block the site with a warning.
Issued by
The certificate authority that signed it, for example Let's Encrypt.
Chain
Browsers need the path from your certificate to a trusted root. If the server leaves out an intermediate certificate, some browsers and apps fail.
Host name
The certificate lists the names it is valid for. The address you visit must be one of them; a wildcard such as *.example.com covers one level.
Protocol
The TLS version used for the connection. TLS 1.2 and 1.3 are current; older versions are switched off in modern browsers.

Want this checked automatically and get alerted?

Centoculus checks your site every 5 minutes on the free plan and alerts you by email and in the app before your customers notice. 50 website monitors and 5 SSL checks a day, free, commercial use allowed. Sign-up opens soon: get early access and you start first.

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Questions about SSL certificates

What happens when an SSL certificate expires?

Browsers show a full-page security warning, and most visitors leave. Apps and other services that call your site stop working, because they refuse the connection.

How do I check the expiry date?

Enter the domain above. The checker shows the date and the days left. In the browser you can also click the lock icon next to the address and open the certificate details.

How early should I renew?

Automatic renewal usually starts about a month before expiry. Renew by hand at least two weeks before, so there is time to fix a failed renewal. A monitor warns you before the date, so you never find out from a visitor.