What Is an SSL/TLS Certificate?

What does an SSL/TLS certificate do?

Modern websites use TLS to encrypt data exchanged between a browser and a server. The certificate helps the browser verify that the server is authorised to use the domain named in the certificate. The older term SSL is still common, although current secure connections use TLS.

Why HTTPS matters

HTTPS helps protect information in transit from interception or tampering. It is important for login forms, contact forms, online shops, and generally any website. A certificate does not prove that a business is trustworthy or that every part of a website is secure.

Common certificate types

Domain Validation (DV) certificates verify control of a domain. Other certificate validation levels may verify additional organisation details, depending on the certificate authority and product. The right choice depends on your site's requirements and the services available from your provider.

Installation and renewal

Many hosting platforms can issue and renew certificates automatically. After activation, check that the site loads over HTTPS and that internal resources do not cause mixed-content warnings. Keep renewal and domain validation working so the certificate does not expire unexpectedly.

If the browser shows a warning

Check the certificate's expiry date, domain name, installation chain, and server configuration. A warning may also occur if the system clock is incorrect or the page loads insecure resources. If your hosting provider manages certificates, contact support with the exact browser error.