Understanding Wildcard SSL and How Does a Wildcard Certificate Work?

Last updated on June 23rd, 2022 at 04:29 am

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A wildcard SSL certificate is an especially adaptable security authentication for encrypting a site and an endless number of sub-domains.

A wild card certificate is a digital certificate that is applied to a domain and all its sub-domains.

Secure Sockets Layer (SSL) certificates often use wildcards to extend SSL encryption to sub-domains.

Extending a single certificate to sub-domains rather than purchasing separate certificates can save money and make administration easier.

The disadvantage, however, is that if a certificate has to be revoked on all others as well.

Purchasing separate certificates may cost a bit more and require more administration, but it also ensures that each sub-domain is individually protected.

Understanding wild card SSL certificates

To better understand what a wildcard SSL certificate is, we will need to understand the difference between a domain and a sub-domain.

A domain is a website address. An example is ‘xyz.com’, this will direct you to its website without the need to type in its IP address.

A sub-domain is a website that is owned by a domain but is separate from the website itself. A sub-domain is utilized for a wide range of purposes, for instance, e-commerce business. An example of a sub-domain is ‘secure.xyz.com’. A sub-domain is created by using an asterisk ‘*’ before the domain with a set of words. A sub-domain can be entire to the root domain website

Here are some benefits and advantages of a wildcard SSL certificates

  • Cheaper: Wildcard SSL certificates are money savers. When you purchase the cheapest wildcard SSL certificate, it will save you money. When you have several sub-domains in need of securing it can get costly purchasing an individual SSL certificate for each subdomain. Not only that, but the server costs for individual IP addresses for each SSL certificate and domain pair need to be considered too.

Purchasing a wildcard certificate to cover all sub-domains eliminates these costs.

  • Easy management: If you purchase an individual for each sub-domain, each SSL certificate will be installed on your server, taking up much more time than is necessary. When the SSL certificate is up for renewal, you only need to renew the single Wildcard SSL certificates, again saving time.

Here are some its advantages of wildcard SSL:

  • It is flexible 
  • Cost-effective
  • Ease of certificate management
  • Cost savings in terms of both certificate purchase and management
  • Future-proofing your website

There are a few disadvantages of a wildcard SSL certificates

  • There are not available at all validation levels.

You can get wildcard at domain validation (DV) and organization validation (OV), but not extended validation (EV). This automatically means that if you want to get an EV certificate on a sub-domain, you’ll have to use single certificates or a multi-domain certificate.

  • When the key gets compromised on one domain or sub-domain, it’s now compromised on the entire sub-domains its installed on. This amplifies the arise of a problem.
  • There are more domains and sub-domains on which you have an installed key. Using parallel attacks that launch requests across all the endpoints using that key pair, there have been exploits demonstrated that can compromise private keys. This creates a disaster in terms of SSL.
  • A common misconception that wildcards secure all sub-domains.

That’s only partially true; these certificates secure all the sub-domains at the first level. Wildcards are much more difficult to deploy on second and third level sub-domains. A better route would be to use a multi-domain wildcard SSL certificate.

Here are some of the steps you should look follow after you have purchased a wildcard SSL certificate; 

  • Subsequent to buying a Wildcard SSL, produce an SSL certificate signing request with the reference bullet before your Website name (ex: *.domain.com).
  • The certificate authority (CA) will then issue an SSL certificate and send it via email with the common name.
  • Name *.domain.com that secures all sub-domains at the first level.
  • Follow the Installation rules and build your webserver effectively to utilize the certificate.

How a wildcard works both in theory and in practice:

A) Securing unlimited sub-domains

A wildcard is an SSL certificate that allows all the sub-domains at one level to be encrypted with the main domain.

Typically, an SSL certificate will only protect a single sub-domain. for instance, in the event that your SSL certificate is for www.maindomain .com, at that point it won’t work for blog.maindomain.com

With a wildcard certificate (*domain.com) you are assured that all your sub-domains on your main domains can be secured. Here are some examples of first level sub-domains which can be secured with the same wildcard and with no limit. 

  • mail.domain.com
  • login.domain.com
  • dev.domain.com

Here are also some examples of the second level sub-domains (*.mail.domain.com). You may need an additional wildcard to encrypt the sub-domains on this level, along with one to encrypt at the first sub-domain level.

  • Member.mail.domain.com
  • Login.mail.domain.com
  • Dev.mail.domain.com

B) Setup

From a technical standpoint, it comes down to the generation of CSR. The certificate authority issues you an SSL certificate in which the common name is filled as *your domain.com. It also includes a Subject 

All you need to do is purchase a wild card character for your domain, like this *domain .com  

How much does a wildcard SSL certificate cost?

The cost of a wildcard SSL certificate differs depending on a few different factors, including:

  • The issuing certificate authority(CA)
  • The brand of SSL certificate
  • The certificate levels of validation
  • The warranty and other benefits that may come with it.


Wildcard certificates are categorized on the basis of the validation level, number of domains, and the number of servers it can be used with. It is always good to go with a cheap SSL certificate before you decide to purchase any type of SSL certificate.