What Is a Multi Domain SSL Certificate?

A multi domain SSL certificate is used to secure and encrypt multiple domain names and servers. In today’s world, the protection of data that is transmitted over the internet has become a top priority for website administrators and owners.

One of the most important aspects of safeguarding sensitive information has been the implementation of SSL Certificates, also known as TLS Certificates.These TLS Certificates encrypt data exchanged between web servers and browsers used by visitors of the webpage, while preventing unauthorized access and cyber-eavesdropping.

This begs the question – what happens when a single SSL certificate needs to secure multiple domains and servers? This is where the Multi Domain SSL Certificates come in to play, they are a versatile solution created to address the security needs of modern websites with more complex domain configurations. 

In this article, we explore the features of Multi Domain SSL Certificates, the benefits they present, and reasons why website owners should consider implementing them.

What is a Multi Domain SSL Certificates

An SSL Certificate is a digital key which creates a secure connection between a web server and a browser. It makes it harder for hackers to intercept and steal data by authenticating websites and encrypting data transferred between a client’s device and the website’s server.

SSL certificates contribute to cyber threat prevention, online transaction privacy and information security, by encrypting sensitive data. This includes payment details, login credentials, and other personal information of the user.

A multi domain SSL certificate is also known as a SAN Certificate (Subject Alternative Name), or as a UCC (Unified Communications Certificate), is explained in more detail below.

Functions of SSL Certificates

SSL Certificates are significant in the protection and security of a website, while ensuring user trust. Offering websites a range of advantages, here are some of the functions of SSL Certificates: 

  • To protect sensitive information, an SSL encrypts data transferred between a user’s browser and the web server.
  • Websites that have SSL certificates utilize the “https://” protocol in the URL and show a padlock icon to indicate that the user is connected securely.
  • SSL ensures data integrity by guarding against unauthorized changes to data while it is being transmitted.
  • By confirming the legitimacy of websites, SSL certificates also aid in the prevention of phishing assaults by making it more difficult for con artists to mimic trustworthy websites.
  • The certificates keep users from seeing warnings about insecure websites when entering data, therefore offering a positive user experience.
  • Websites with SSL certification may rank higher on search engines, which increases their visibility in search results.
  • SSL Certificates are essential for protecting payment information, promoting consumer confidence, and securing online transactions on e-commerce websites.
Multi Domain SSLs Provide Enhanced Flexibility

The Need for Multi Domain SSL Certificates

Many businesses today operate multiple websites and subdomains, or alternative domain names. The traditional approach of securing each domain with an independent SSL Certificate may not be practical and cost-efficient. 

Multi Domain SSL Certificates address this issue by presenting a convenient solution to securing multiple domains or subdomains, by using a single certificate. This provides enhanced flexibility and efficiency in managing website security.

Challenges Facing Traditional SSL Certificates

Difficult Process

Obtaining and maintaining individual SSL certificates for every domain or subdomain can be a labor-and time-intensive task.

Potential Expense

Purchasing separate SSL certificates for several domains can get expensive, especially for businesses that maintain many online assets.

Maintenance Overhead

When there are several certificates, there is an increase in the complexity of ongoing tasks such as certificate renewal and management, which results in an administrative burden.

Inconsistency in Security Configurations

A unified security posture may be difficult to maintain if different SSL certificates are managed for every domain, which could lead to inconsistent security configurations.

Administrative Burden

IT teams’ administrative workload is increased by having to track and handle numerous certificates across multiple domains, which may influence operational effectiveness.

Problems with Scalability

Keeping track of individual SSL certificates becomes more difficult as the number of domains or subdomains increases.

Features and Benefits of Multi Domain SSL Certificates

Individuals and organizations can reduce costs, meet a variety of security requirements, and avoid the difficulties of managing traditional SSL certificates, by unifying several domains, subdomains and servers, under a single certificate. The benefits and features of Multi Domain SSL Certificates, include: 

Consolidated Management

Organizations can combine their efforts to manage SSL certificates by using multi domain SSL certificates. Management operations, such as certificate issuance, renewal, and installation, are made more efficient by using a single certificate which protects up to a hundred* domains or subdomains.

* Figure at time of writing blog post

Simplified Process

Having a single certificate streamlines management as mentioned above, thereby improving operational efficiency and resources.

Financial Savings

Purchasing multi-domain SSL certificates is significantly more affordable than obtaining separate certificates for every domain or server.

IT Efficiency

IT teams can become streamlined and save time thanks to a multi domain SSL Certificate management’s efficiency. Administrators and staff can allocate resources more effectively and concentrate on other crucial duties when they have fewer certificates to handle.


Multi domain SSL certificates are appropriate for businesses of all sizes and sectors, as they address a broad spectrum of security requirements. Whether managing a portfolio of e-commerce websites, intranet portals, or a combination of public-facing and internal web applications. The certificates provide the flexibility to secure diverse domain configurations under one umbrella.


The flexibility of multi domain SSL certificates allows organizations to adapt their security strategies to meet evolving business requirements. With the ability to secure multiple domains and servers under one certificate, organizations can easily scale their security measures as their web presence or operation grows.

Reduce Costs and Admin With a Multi Domain SSL

Types Of Multi Domain SSL Certificates

Multi Domain SSL Certificates exist in different forms, while accommodating for different purposes. Here are some common types and their functions: 

Unified Communications Certificates (UCC)

UCC certificates are specifically created for use with Microsoft Exchange Server and Microsoft Office Communications Server environments. These allow you to secure multiple domain names, subdomains, and hostnames associated with Exchange Server or Office Communications Server under a single certificate, supporting up to 100 domain names or subdomains.

Subject Alternative Name (SAN) Certificates

SAN certificates are also referred to as Unified SSL certificates and allow you to secure multiple domain names and servers under one certificate. They are versatile and can be used for a range of applications, including securing e-commerce websites, corporate intranets, and public-facing web applications.

Wildcard Multi Domain SSL Certificates

These types of SSL Certificates combine the functionality of multi domain SSL Certificates with wildcard SSL certificates. They allow you to secure multiple domain names and their subdomains using one certificate, securing them with a wildcard character (*).

Extended Validation (EV) Multi Domain SSL Certificates

EV Multi Domain SSL Certificates offer the highest standard of validation and trust, as they require rigorous verification of the requesting organization’s identity. These certificates allow an organization to display its name prominently in the browser’s address bar, to indicate the high level of security and trustworthiness.

Buy a Wildcard Multi Domain SSL Now

How To Get A Multi Domain SSL Certificate

Obtaining a Multi Domain SSL Certificate is fairly similar to how one would get a traditional SSL Certificate. However, here are more considerations, here is a general overview of the process involved: 

  1. Choose a reputable Certificate Authority (CA) – Research and select a CA with a good reputation that offers Multi Domain SSL Certificates.
  1. Select a Certificate Type – Select the type of Multi Domain SSL Certificates you need based on your requirements.
  2. Provide Domain Information – Prepare a list of the domain names and subdomains you wish to secure, using your certificate. Ensure that you have control over each of the domain names you list and can verify ownership during the certificate issuance process.
  3. Generate a Certificate Signing Request (CSR) – Create a CSR for your primary domain name and include the additional domain names and SANs in the CSR, to specify which domains should be covered by the Multi Domain SSL Certificate.
  1. Submit CSR and Domain Verification – Submit the CSR to the CA accompanied by all documentation required for domain verification. The CA will verify your ownership over each of the domain names listed in the CSR before issuing the certificate.
  2. Certificate Issuance and Installation – After verification, the CA will issue the Multi Domain SSL Certificate. Download the certificate files and install them on your web server by following the CA’s instructions or make use of your hosting provider’s management tools.
  3. Configure Web Server – Configure your web server to use the Multi Domain SSL Certificate for all domains and subdomains listed in the certificate. This is done by updating your server’s SSL/TLS settings.
  1. Test SSL Installation – Be sure to test the certificate to ensure it is configured correctly and provides a secure connection for all specified domains.
  2. Renewal and Maintenance – Monitor the expiration date of your certificate and be sure to renew it before it expires to maintain continuous security coverage for all your domains. You can set up reminders or automatic renewal services provided by your CA.

How Multi Domain SSL Certificates Work

While they are referred to most commonly as Multi Domain SSL Certificates, they are also known as Unified Communications Certificates (UCC) or Subject Alternative Name (SAN) certificates.

Subject Alternative Names (SANs)

Multi domain SSL Certificates are able to secure multiple domain names (including primary and subdomains) thanks to Subject Alternative Names (SANs), which are additional domain names that are included within the certificate’s Subject field.

When generating a Multi domain SSL Certificate, users need to specify the list of domain names or SANs that they need to secure. These can include domains with different top-level domains (TLDs), variations of the primary domain name and sub domains.

Encryption and Security

Much like traditional SSL Certificates, Multi Domain SSL Certificates use encryption algorithms to secure communication between the web server and the user’s browser. When a visitor accesses any of the domains listed in the certificate, their browser will verify the authenticity of the certificate and establish a secure connection to the web server.


  • SSL Certificates play a critical role in safeguarding sensitive information transmitted over the internet by encrypting data exchanged between web servers and browsers.
  • Managing individual SSL certificates for each domain can be labor-intensive and expensive, leading to administrative burdens and scalability issues.
  • Multi Domain SSL Certificates provide a solution for securing multiple domains or subdomains under a single certificate.
  • These kinds of certificates simplify security management by consolidating certificate issuance, renewal, and installation, leading to cost savings, operational efficiency, and versatility in securing various domain configurations.
  • Obtaining a Multi Domain SSL Certificate involves selecting a Certificate Authority, providing domain information, generating a Certificate Signing Request (CSR), and submitting the CA for verification.


What is the difference between a Multi Domain SSL Certificate and a Wildcard SSL Certificate?

While both types of certificates can secure multiple subdomains, however a Multi Domain SSL Certificate allows you to cover individual domain names, as well as their subdomains under a single certificate. Meanwhile, a Wildcard SSL Certificate secures a primary domain and all its subdomains with a single certificate using a wildcard character (*).

How many domains can be secured with a Multi Domain SSL Certificate?

The number of domains that can be secured by a Multi Domain SSL Certificate depends on the specific certificate type and the Certificate Authority providing it. Some certificates might support a limited number of domains, while others may offer additional domain slots. Currently it appears that the limit is a hundred.

Can I add or remove domains from a Multi Domain SSL Certificate after it has been issued?

This is dependent on the policies of the Certificate Authority and the type of certificate you have obtained. Some CAs may allow you to add or remove domains during the validity period of the certificate, while others will require you to purchase a new certificate with the updated domain list.

Do all web servers support Multi Domain SSL Certificates?

Most current web servers, such as Apache, Nginx, and Microsoft IIS, support Multi Domain SSL Certificates. Despite this, it is important to ensure that your server and SSL/TLS configuration are compatible with Multi Domain SSL Certificates before purchasing and installing one.

Can I use a Multi Domain SSL Certificate for email encryption and secure communication?

While Multi Domain SSL Certificates are primarily designed for securing web communication, they can also be used for email encryption and secure communication protocols such as SMTP, IMAP, and POP3, depending on your email server software.

Do Multi Domain SSL Certificates provide the same level of security as single-domain certificates?

Yes, Multi Domain SSL Certificates provide the same level of encryption and security as single-domain certificates do.

Other Blogs of Interest:

A Simple Explanation Of SSL Certificate Errors & How To Fix Them

How To Renew SSL Certificates For A Website

Web Hosting Security – Top 11 Best Practices

7 Factors for Choosing Web Hosting Services for your Small Business

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