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How to Pick the Right SSL Certificate for your Subdomain?

Posted DateApril 5, 2022
Posted Time 4   min Read

Today, flagging websites as ‘Not Secure’ is an organization’s worst nightmare. Such warnings don’t inspire trust or confidence among customers, leading to high bounce and attrition rates. Websites lose search engine rankings. This has necessitated SSL certificates.

But the website is only fully protected if SSL secures the domain and all subdomains. Standard SSL certs only cover one domain and buying such certs for each subdomain is an expensive affair. So, what is the right SSL certificate for subdomains? What considerations should you make while buying SSL for subdomains? Keep reading to find out.

Understanding Subdomains

As the name suggests, the subdomain is a sub-division of the main/ parent domain in the Domain Name System (DNS) hierarchy. It is also referred to as the child domain.

Subdomains ensure greater ease of website navigation. They help organize websites by logically separating them into different sections. Subdomains are also used by organizations to host different, but related websites.

The Subdomain Structure

The subdomain structure contains the top-level domain (TLD), main/ base domain, and the first-level subdomain. We can understand the subdomain structure by going from left to right in accordance with the DNS hierarchy.

  • .com is the TLD
  • example is the main/ base domain
  • is the root domain or second-level domain
  • is the third-level domain or sub-domain

Subdomains come in multiple levels too. For instance, organizations may have the following first-level subdomains:


Second-level subdomains could be:


Third-level subdomains could be:


Why Do Subdomains Need to Be Protected with SSL? 

SSL certificates for subdomains, like any SSL certificate, enable organizations to authenticate their identity, establish secure server-browser communication channels and ensure data privacy, integrity, and security.

Without subdomain SSL, attackers have an opening to intercept communications through the subdomain. This makes the website vulnerable to man-in-the-middle attacks, eavesdropping attacks, malware attacks, phishing, etc. Further, search engines flag subdomains without SSL security as ‘Not Secure.’

Choosing the Right SSL Certificate for Subdomains

Types of Subdomain SSL

1. Wildcard SSL:

It is an SSL certificate for all subdomains at the same level. It allows organizations to secure one domain and multiple subdomains at the same level using a single certificate. You need to denote the main domain and list the subdomain with the * (Asterix) symbol to secure them.

Further, all subdomains at this level can be added/removed to the certificate hassle-free. They are inexpensive and much easier to manage. However, they are only available as Domain Validation (DV) and Organizational Validation (OV) Certs. It is impossible to get Extended Validation for Wildcard SSL due to their open-ended nature.

Note that subdomains need to be at the same level, and a single wildcard certificate cannot secure different levels of subdomains. If you want to secure subdomains of another level, you must buy another WC cert listing the first-level subdomain as the main domain and the next-level as subdomains.

2. Multi-Domain SSL or SAN Certificates 

These SSL certificates allow organizations to secure multiple domains and subdomains using a single certificate. Here, organizations can list their subdomains, domains with other TLDs, etc., as Subject Alternate Names (SANs). You can secure 250 or more domains and sub-domains with a single certificate based on the SSL Cert provider chosen.

Multi-domain certs are available in all three levels of validation – EV, OV, and DV. Though these certs are easy to manage and inexpensive when chosen from the right provider, one cannot add or remove domains and subdomains by oneself; the cert would have to be reissued.

Key Considerations While Choosing SSL Certificates for Subdomains

1.The Right Certificate Authority (CA)

SSL cert providers or CA you choose must be reputable and trustworthy since rogue and insecure certificates are rising. Also, consider the encryption strength of certs, additional security features, total cost (including maintenance, reissue, renewals, etc.), support, etc., while choosing your CA.

2. Subdomains and Their Levels 

If you have subdomains at different levels, you should choose multi-domain SSL. If you have a single domain and multiple subdomains at the same level, Wildcard SSL is best-suited.

3. Level of Validation 

Based on the level of validation and assurance required, you can choose between OV, EV, and DV certs. If you have a dynamic website, an e-commerce website, or other websites that collect sensitive user information, it is best to choose EV multi-domain SSL. Unless you have a simple blog or a static website, you should not choose DV certs.

4. Should You Choose a Multi-Server SSL?

It is best to avoid multi-server SSL certificates for subdomains as it duplicates keys, making the website vulnerable.

5. Certificate Management Features 

Choose subdomain SSL certificates from CAs that offer solid and hassle-free Certificate Management Systems. The CMS must assure full visibility, real-time insights, and ease of use.

The Bottomline 

Given the popularity of subdomains, SSL Certificates for subdomains are indispensable. Make the right choice, better protection, page experiences, and search engine rankings. If you are still in doubt, it is worth considering Indusface, which offers High-cadre Class-3 certificates i.e., OV and EV SSL certificates from Entrust.

Create positive web presence and win the trust of customers with right SSL Certificate!

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