Modern TLS certificates rely on the Subject Alternative Name (SAN) field rather than the outdated Common Name. Browsers now require SAN to specify which hostnames and IP addresses a certificate protects. This shift supports complex architectures, allowing a single certificate to secure multiple domains, subdomains, and distinct addresses, moving beyond the limitations of single-host validation.

SANs enable true multi-domain certificates, essential for environments using reverse proxies, containers, or cloud infrastructure. A wildcard certificate only covers subdomains, leaving the root domain and unrelated domains exposed. By consolidating various entries—like example.com and example.net—into one certificate, organizations can efficiently manage white-label applications, multi-tenant systems, and diverse client domains without juggling numerous individual files.

Combining SAN with Server Name Indication (SNI) allows hosting multiple HTTPS sites on a single IP address, vital for shared servers and cloud environments with limited resources. This approach streamlines operations significantly. Administrators handle fewer renewals and configurations, reducing the risk of expiration errors and operational failures. Centralizing management also simplifies automation tools like ACME/Let's Encrypt for cleaner, more predictable infrastructure.

However, consolidation carries risks. Certificate Authorities impose SAN limits, and a failed validation for one domain can block the issuance or renewal of the entire certificate. Revoking a compromised certificate impacts every associated domain. While SANs are ideal for shared infrastructure and SaaS platforms, highly segregated environments might prefer separate certificates to maintain strict isolation and minimize blast radius during security incidents.