Wildcard SSL Certificates: When You Need One

What a Wildcard Certificate Covers

A wildcard SSL certificate secures a domain along with an unlimited number of its first level subdomains under a single certificate. Rather than purchasing and managing separate certificates for each subdomain, one wildcard certificate covers your main domain and every subdomain in that structure automatically.

How Wildcard Coverage Works

A wildcard certificate issued for a domain covers that domain itself along with any subdomain directly beneath it. Additional subdomain levels beyond the first typically require either an additional wildcard certificate at that specific level or a separate certificate entirely, depending on your exact subdomain structure.

Who Needs a Wildcard Certificate

Wildcard SSL makes sense for businesses running multiple subdomains under one main domain, such as separate subdomains for a blog, a customer portal, a support system, or a staging environment. Rather than managing individual certificates for each of these, a single wildcard certificate covers them all under one purchase and one renewal date.

Managing New Subdomains

One of the most practical advantages of a wildcard certificate is that adding a new subdomain in the future does not require purchasing or installing a new certificate for it, since the existing wildcard certificate already covers it automatically. This is particularly valuable for businesses that expect to add subdomains over time without wanting to manage certificates individually for each one.

Security Considerations

Because a single wildcard certificate's private key covers every subdomain under that domain, if that private key were ever compromised, every subdomain covered by the certificate would be affected simultaneously. Businesses with particularly sensitive subdomains sometimes choose separate certificates for those specific subdomains rather than including them under a shared wildcard, isolating potential risk.

Wildcard vs. Multi-Domain Certificates

If your situation involves securing entirely separate domains rather than subdomains of one main domain, a wildcard certificate is not the right fit. See Multi-Domain (SAN) SSL Certificates Explained for the certificate type designed specifically for that scenario.

Installing Your Certificate

Once issued, installing a wildcard certificate follows a similar process to standard certificates, though your certificate signing request needs to be generated specifically for the wildcard domain format. See Generating a CSR (Certificate Signing Request) for details.