SSL Certificate

An SSL certificate is a digital credential that enables HTTPS, encrypting the connection between a browser and a server and verifying the site's identity.

When a site has a valid certificate, traffic travels over HTTPS instead of plain HTTP. The certificate, issued by a certificate authority, does two things: it lets the browser and server establish an encrypted channel so data in transit cannot be read or tampered with, and it confirms that the site is who it claims to be for the domain. Browsers show a secure connection rather than a "Not secure" warning, which builds user trust. Strictly the modern protocol is TLS, but the term SSL certificate remains in common use.

HTTPS is a confirmed, if lightweight, Google ranking signal, and just as important, browsers now warn users away from sites without it, especially on pages with forms or logins. For SEO the certificate is effectively a baseline requirement rather than an optional extra. A site without one looks untrustworthy to both users and search engines.

Moving to HTTPS is itself a site migration and needs the same care. Every HTTP URL should 301 redirect to its HTTPS version, internal links and canonical tags should point at the HTTPS URLs, and the sitemap should list them. Certificates also expire and must be renewed; an expired or misconfigured certificate triggers a browser warning that can block visitors entirely and harm crawling. Automated renewal and monitoring prevent that lapse.

Related: Site Migration, Security Issues, HTTP status codes reference