What is an SSL certificate?

An SSL certificate is a digital file that proves a website's identity and lets a browser set up an encrypted connection, shown as HTTPS. Today the encryption is technically called TLS, but the name SSL certificate stuck.

What does an SSL certificate contain?

The names it covers, the public key, the authority that issued it and the dates it is valid from and until. A browser checks that the name matches the site, that the dates are current and that the issuer is trusted. If any check fails it shows a full-page warning.

Why do SSL certificates expire?

A limited life means that a stolen or mistakenly issued certificate stops working eventually and that identity checks repeat. Public certificates are being limited in stages to 200 days from March 2026, 100 days from March 2027 and 47 days from March 2029, so renewal has to be automatic and watched.

How do I check one?

Use the SSL certificate expiry checker or read the guide to fixing an expired certificate.

Where Datumboard fits

Datumboard puts the signals behind this in one dashboard for your client sites and side projects. It is in early access, and you can join the list below.