What is a wildcard certificate?

A Wildcard SSL certificate is used to secure unlimited sub-domains within the same level that share a common base domain.

For example: A Wildcard certificate issued to “*.mydomain.com” can be used to secure the following domains:

- login.mydomain.com
- secure.mydomain.com
- support.mydomain.com
- www.mydomain.com etc.

Along with multiple subdomains, a Wildcard SSL will also secure the bare domain mydomain.com.

Note! Comodo (now Sectigo) certificates issued for *.sub.mydomain.com will also secure sub.mydomain.com, while other brands will secure only subdomains of sub.mydomain.com.