Subject Alternative Name (SAN) is a certificate field that lists additional identities a certificate is valid for, such as hostnames or other names. It matters because certificate trust must match the actual identities a system is trying to verify, not just a vague or outdated subject field.
What is Subject Alternative Name (SAN)?
SANs let one certificate represent multiple names, which is common in modern TLS deployments. Correct SAN handling is important because relying parties check whether the presented certificate is actually valid for the name the user or system intended to reach.
What Subject Alternative Name (SAN) Commonly Supports
Common uses include multi-host certificates, service aliases, internal service naming, and modern certificate validation workflows.
Subject Alternative Name (SAN) vs. Single-Identity Certificate Binding
SAN enables one certificate to bind multiple names explicitly. Single-identity binding covers only one name or a narrower trust scope.
Frequently Asked Questions
Why are SANs important?
Because name mismatches can break trust or create confusing and unsafe certificate behavior.
Can SANs replace secure key handling?
No. They affect identity binding, but private-key protection and certificate lifecycle controls still matter.
