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What is a Wildcard SSL Certificate?

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Securing subdomains is easy when you use a Wildcard SSL Certificate

There was a time when encrypting sub-domains meant getting one certificate for every subdomain. That time is long gone. Wildcard SSL certificates can do it all at once. What is a wildcard certificate? Let’s start at the top…

What is a Subdomain?

To explain what Wildcard SSL certificates do, we need to start by explaining URLs and what a subdomain even is. Here are the three main url components that come into play for ssl certificates:

  1. Top-Level Domain. The Top-Level Domain or TLD is the small portion at the root of a URL. Typically two or three letters (such as .com or .uk), the Top-Level domain can indicate country of origin or a generic top-level.
  2. Domain. The Domain is typically considered the name of the website. For instance, Google’s website is at The name of this domain is ComodoSSLStore.
  3. Sub-Domain. Sub-Domains are situated before the main domain in the URL. Technically, WWW. is a sub-domain. Most SSL certificates protect both WWW and non-WWW domains.

Sub-Domains can be used for a variety of things. You can host a blog at one, set up a members’ area, an FTP server, a mail server—really anything you need. Situated ahead of the Domain name in a URL, subdomains typically look like this:


What is a Wildcard Certificate?

A wildcard certificate makes it simpler and cheaper to secure all of the subdomains on your website. Let’s say your website has 5 different subdomains:


With a traditional SSL certificate, you’d have to buy and install 5 different certificates to secure all these sites. With a wildcard SSL certificate, you can purchase and install just one certificate to secure all 5 websites!

What is a wildcard ssl certificate? SSL for Subdomain

Encrypting your domain and all of its accompanying sub-domains – as many as you have – is easily accomplished with a single Wildcard SSL certificate.

Wildcard SSL Certificate

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How a Wildcard SSL Certificate Works

Before your SSL certificate is issued, you must generate a Certificate Signing Request. This is like an application for your SSL certificate. The CA will check against the information you provide to validate you, and will include that information in your certificate details. So it’s very important you get it right.

Where Wildcard SSL differs from traditional SSL is in the Fully Qualified Domain Name field. Typically you list the exact URL of the website you’re encrypting. With Wildcards you put an asterisk at the sub-domain level you want to encrypt. Like this: * Once the certificate issued it encrypts all sub-domains at the designated level.

An SSL Certificate that Grows with You

The best part of Wildcard SSL is that it is essentially future-proof. If you ever add a sub-domain during your Wildcard SSL certificate’s lifespan, simply reissue the certificate and re-install it. From that point, it will cover the new sub-domain as well.

Encrypting individual sub-domains would be outrageously expensive. Don’t let it be! Investing in a Wildcard SSL certificate saves time and money.