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Heroku offers the option to use Hostname based SSL. Apparently this is a solution which they use to offer multiple SSL hostnames on the same IP address, without using SNI (which doesn't work on Windows XP).

From the website:

Hostname based SSL works with all browsers. Use it when you will be accessing you site via SSL on a subdomain such as, or * Hostname based SSL will not work with root domains as it relies on CNAME aliasing of your custom domain names. CNAME aliasing of root domains is an RFC violation.

So how exactly does this work? Does it mean that they request you to add a CNAME alias to your domain and then issue a certificate for the CNAME (e.g. ->, upon visiting, a certificate for is presented). Does such a thing work? If it does not do that, then what does it do?

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closed as off topic by random Aug 28 '11 at 21:16

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In SSL, CNAMEs are never checked - only the hostname entered by user is considered. – grawity Dec 20 '10 at 16:21