What sub-domains can I secure with a Wildcard SSL Certificate?

Wednesday, April 26th, 2017

A Wildcard SSL Certificate is specifically created to allow users to secure one single domain name and all its sub-domains. With other words, you can secure one single domain name and an unlimited number of sub-domains belonging to that domain name with one single Wildcard SSL Certificate.

You can add sub-domains to your server and they will be covered by your Wildcard SSL Certificate automatically. You do not need to re-issue your Wildcard SSL Certificate each and every time when you add sub-domains to it. The newly added sub-domains will be automatically covered by your Wildcard SSL Certificate.

NOTE: The sub-domains that you can secure with one Wildcard SSL Certificate have to be either 1st level sub-domains (e.g.: *.example.com) or 2nd level sub-domains (*.mob.example.com). You cannot secure 1st and 2nd level sub-domains with one regular Wildcard SSL Certificate.  If you want to secure 1st level sub-domains and 2nd level sub-domains, you have to get a Multi-Domain Wildcard SSL Certificate, or 2 separate Wildcard SSL Certificates.

For example, a regular Wildcard SSL Certificate allows you to secure:

  1. One main domain name (example.com) and all its 1st level sub-domains (*.example.com):
    1. my.example.com
    2. test.example.com
    3. dev.example.com
    4. mail.example.com
    5. (etc)
  2. Or, one sub-domain (mob.example.com) and all 2nd level sub-domains (*.mob.example.com):
    1. my.mob.example.com
    2. test.mob.example.com
    3. dev.mob.example.com
    4. mail.mob.example.com
    5. (etc)

In order to secure one domain and all its sub-domains as shown in the first example, you have to include *.example.com as a common name (domain name) when creating a CSR (Certificate Signing Request). If you want to secure 2nd level sub-domains, then you have to enter *.mob.example.com as a common name (domain name) when creating a CSR (Certificate Signing Request).