A multi-domain SSL certificate is a digital security certificate designed to secure multiple different website domain names with a single certificate.
According to Nexcess, a multi-domain SSL certificate is structurally the same as all other certificates. Its key function is to allow for a single unique IP address for multiple domain names. How it works is that a primary SSL certificate is issued with additional alternative domains listed on the same certificate.
How a Multi-Domain Certificate Works
Unlike standard SSL certificates that typically protect just one domain or a domain and its direct subdomains (like a wildcard certificate), a multi-domain certificate uses a feature called Subject Alternative Names (SANs).
- Primary Domain: When you get a multi-domain certificate, you specify one main domain name (e.g.,
yourcompanymain.com). This is often referred to as the Common Name (CN). - Subject Alternative Names (SANs): You then list the additional domain names you want to secure under the same certificate as SAN entries. These can be completely different domain names.
This setup means that browsers and devices checking the certificate for any of the listed domain names will see the same valid certificate, confirming the identity and securing the connection for all of them.
Key Characteristics
Here are the core aspects of multi-domain certificates:
- Secures Multiple, Distinct Domains: Can cover
domain-a.com,domain-b.net,domain-c.org, etc., using one certificate. - Can Secure Subdomains: Can also secure subdomains like
shop.domain-a.comorblog.domain-b.net. - Secures Different TLDs: Can include domains with different top-level domains (e.g.,
.com,.org,.net). - Flexible Management: Allows you to manage multiple websites' security under a single renewal schedule.
- Potential Cost Savings: Often more cost-effective than buying separate certificates for each domain, especially when securing many domains.
Example
Imagine a company managing several related websites:
| Website URL | Purpose | Included on Certificate? |
|---|---|---|
mycompany.com |
Main corporate site | Yes (Primary Domain) |
shopmycompany.net |
Online store | Yes (SAN) |
blog.mycompany.com |
Company blog | Yes (SAN) |
mycompanysupport.org |
Customer support portal | Yes (SAN) |
A single multi-domain certificate could secure all four of these distinct URLs, providing encrypted connections for visitors to each one.
Benefits
Using a multi-domain certificate offers several advantages:
- Simplified Management: Reduces the administrative burden of managing multiple certificates.
- Cost Efficiency: Often cheaper than purchasing many individual SSL certificates.
- Consolidated IP Usage: As mentioned by Nexcess, they facilitate the use of a single IP address for multiple domain names.
- Flexibility: Easily add or remove domain names from the certificate as your web presence changes.
In essence, a multi-domain certificate is a versatile security solution that streamlines the process of securing a portfolio of different website domains under one roof.
