SSL certificate

Definition

An SSL certificate is the common name for a digital certificate used to authenticate a hostname during TLS.

How it works

The certificate bundles a public key with the domain names it covers, the issuing authority, and validity dates. During the TLS handshake, your server presents it and the visitor's browser checks the chain of trust before any encrypted traffic flows. "SSL" survives purely as the popular name — every certificate issued today is used with TLS.

Example: A certificate for example.com covers only the names listed in it, not every subdomain or unrelated domain you own.

Often confused: SSL is the legacy protocol name; current secure web connections use TLS, although "SSL certificate" remains the common wording.

Related terms

• Certificate authority (CA)
• Certificate signing request (CSR)
• HTTPS
• Transport Layer Security (TLS)

Learn more from Bitfoo

• Review SSL certificate options
• Check HTTPS and redirects

Sources

• IETF RFC 5280: Internet X.509 Public Key Infrastructure
• IETF RFC 8446: The Transport Layer Security Protocol Version 1.3

Last reviewed 2026-07-19.