A wildcard certificate is a public key certificate which can be used with multiple subdomains of a domain.
Depending on the number of subdomains an advantage could be that it saves money and also could be more convenient.
Limitation:
- Only a single level of subdomain matching is supported.
- It is not possible to get a wildcard for an Extended Validation Certificate.
- A workaround could be to add every virtual host name in the Subject Alternative Name (SAN) extension. The major problem being that the certificate needs to be reissued whenever a new virtual server is added.
- Wildcards can be added as domains in multi-domain certificates or Unified Communications Certificates (UCC). In addition, wildcards themselves can have subjectAltName extensions, including other wildcards.