What is a subdomain SSL certificate?

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An SSL certificate for subdomains is often underrated, but it is of great importance. While protecting your main domain is well understood, this need extends to its subdomains as well. It is not just an additional task; it is an important aspect of maintaining the integrity of your site and user trust.

Subdomains, extensions of your main domain that are dedicated to specific content or regional versions of your site, require encryption just like the main domain. Without their protection, sensitive data that users exchange with your site may be vulnerable to interception or manipulation.

So, what are subdomain SSL certificates and what are their benefits?

Table of contents

What is a subdomain?
What is a subdomain SSL certificate?
Do you need a separate SSL for a subdomain?
Types of SSL Certificates for Subdomains
Benefits of Using SSL Certificates for Subdomains
How to get an SSL certificate for a subdomain?
What is a subdomain?
A subdomain is a subdivision of a domain name used to organize and categorize content on a website. It functions as a separate entity from the main domain, with its own unique address and distinct content, design, and users.

Technically, a subdomain is created by adding a prefix to the main domain in the DNS (Domain Name System) settings, which tells web servers to treat it as a separate section of the site.

For example, consider the site “. If you want a separate
section, such as a blog, you can create a subdomain like. This subdomain operates independently of “”, allowing you to host blog-specific content under its own address.

Likewise, you can create other subdomains, such as  for an online store or ” for customer support, each serving a unique purpose within the larger site.

Essentially, subdomains make it easier to organize and manage different sections or features of a site within one main domain, improving navigation and accessibility for users.




What is a subdomain SSL certificate?
An SSL certificate for a subdomain ensures secure communication between the user's browser and the subdomain server, protecting sensitive data from interception or tampering.

If you have multiple subdomains within a single domain, you can use a single wildcard certificate to secure all of your subdomains within a single SSL installation. This wildcard certificate covers an unlimited number of first-level subdomains of the main domain.


Wildcard SSL certificates are ideal for organizations with multiple subdomains or organizations that frequently create new subdomains. They provide full SSL protection for all subdomains within a single domain.

When requesting a wildcard SSL certificate, add an asterisk (*) before your fully qualified domain name (FQDN) when generating your CSR . This is what it will look like in your CSR:

Do you need a separate SSL for a subdomain?
You need a separate SSL certificate for a subdomain if you use a standard SSL certificate for a single domain that does not cover subdomains. A wildcard SSL certificate or a multi-domain SSL certificate can protect multiple subdomains. However, a wildcard certificate has the advantage of protecting an unlimited number of subdomains, compared to a maximum of 250 for multi-domain certificates.

Sometimes you start a site without subdomains, but later add several to expand your content and online presence. In this case, it is cheaper to purchase a Wildcard certificate. This way, you will have additional subdomains whenever you need them, reducing your costs and setup time.