Wildcard SSL Explained for Multi-level Subdomains Security

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Everything you ever wanted to know about wildcard SSL multi level subdomains and securing them.

Those who have never purchased an SSL certificate and those who are still new to the technology might not understand the nuanced differences between different types of SSL products. In recent years, a wide range of SSL products like wildcard SSL, multi-domain wildcard SSL, SAN Wildcard, and UCC Wildcard SSL certificate has been released to meet different needs.

An SSL certificate is used to encrypt and secure the data that’s transmitted from a client to the server and vice versa. Currently, the industry standard for encryption is a 2048-bit RSA key (or 256-bit ECC) for signatures and 256-bit session key for communication.

In most cases, an SSL certificate can only secure a single Fully Qualified Domain Name (FQDN). However, if you own multiple subdomains or domains, you might need to use a Wildcard SSL.

What is Wildcard SSL Certificate?

As we’ve already mentioned, a traditional SSL certificate can only secure a single domain name for a single certificate. However, a Wildcard SSL certificate makes it possible for you to cover the primary domain along with all of its first-level subdomains with a single certificate.

Features of Wildcard SSL

  • There is absolutely no limitation on the number of subdomains you can cover. All of the primary domain’s first-level subdomains are automatically covered and can even be added later during the validity period of the certificate.
  • Offers NIST and CAB Forum standard 256-bit data encryption.
  • A Wildcard SSL certificate is compatible with all modern web browsers and devices.

The only drawback of a Wildcard SSL is that you can only get it for a single primary domain. If you want to secure multiple domains, you need multiple certificates or a multi-domain wildcard.

Types of Domains Secured with Wildcard SSL

Getting a Wildcard SSL certificate for *.website.com will ensure that the following first-level subdomains are also secured:

  • blog.website.com
  • store.website.com
  • mobile.website.com

Plus any other sub-domains that website.com may have on that subdomain level.

What is a Multi-Level Wildcard Certificate?

As mentioned previously, a Wildcard certificate can only secure one primary domain and all its first-level subdomains. Or rather, all of the subdomains on that level of the URL. A URL is organized like this:


A Wildcard will only secure one subdomain level. Generally, most websites only have one subdomain level, so this isn’t a problem. This is also why Wildcards are generally marketed as being for first-level sub-domains.

However, if you get a multi-level Wildcard certificate (also known as a Multi-Domain Wildcard, which we mentioned earlier), you can secure multiple domains along with their subdomains with a single certificate.

Types of Domains Secured through Multi Level Subdomain Wildcard SSL

Let’s say you need to secure two domains — .website.a.com.au and .abc.page.com. In this case, you’ll be able to secure the following subdomains:

  • a.com.au
  • website.a.com.au
  • website.a.com.au
  • abc.page.com
  • abc.page.com
  • abc.page.com

These are just a few variations to highlight that a Multi-Level Wildcard Certificate can secure multiple subdomains for multiple primary domains.


Both Wildcard SSL and Multi-Level Wildcard SSL certificates offer industry-standard 256-bit encryption and 2048-bit root encryption along with immediate issuance and strong customer support.

Users that want to secure multi-level subdomains within a single domain should also consider a Multi-Domain Wildcard SSL certificate, as a standard wildcard will only encrypt sub-domains on that first level.

Other Important Resources Related to Wildcard SSL

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