: Wildcard SSL vs Multi-domain vs multiple single certs Suppose I want to buy SSL certs for a domain, say xyzzy.com and three sub-domains (www.xyzzy.com, smtp. and mail. for example). There seem

@Shanna517

It seems that no one has mentioned about multi domain and wildcard SSL certificate combination here in answer. Now, many third party Certificate Authorities offers this type of certificate and they are known as Multi Domain Wildcard SSL, which helps to protect multiple fully qualified domain name and unlimited sub domains on the multiple servers.

This Multi Domain Wildcard SSL certificate comes with premium layers of securities such as unlimited server licenses, 256 bit SSL encryption, dynamic trust seal, 99% mobile and web browsers compatibility and much more.

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@Shakeerah822

Using multiple certificates makes recovery easier in the event of a compromise of your private key. If you have multiple subdomains across several servers sharing the same certificate (and private key) then all the traffic on all machines is instantly vulnerable once any machine is compromised. It's the 'all your eggs in one basket' problem.

Another thing to consider is whether you plan to use something like AWS's Cloudfront CDN mapped to your own subdomain, which means that you now have to share your private key with AWS to enable it. Using unique certs means AWS only sees the private key unique to one subdomain.

These are more security than technical issues, so you have to weigh how much time it would take to swap certificates across however many subdomains you plan to use. If you only use a few, the difference is tiny (but then so is the price difference). If you plan to use many, the price difference is greater and so is the time spent updating that many more machines or services.

One last note, at time of posting this answer the new Certificate Authority Let's Encrypt will be launching in just under a month, in mid-November 2015, and this will make it possible to generate free certificates. They do not support wildcard certificates (for the reasons outlined above) but if you can wait a few more weeks the pricing becomes a non-issue.

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@Kristi941

From my personal experience, depends if your site/proyect would need or not some extra domains in the short range.
Wildcard Cert will cover all the subdomains, so if your site grows bigger it should end being the most cost effective solution.

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