Clarification using both www subdomains and custom subdomains

This section of the docs states “We strongly recommend that you use a www subdomain” and then goes on to say that “A custom subdomain is a type of subdomain that doesn’t use the standard www subdomain part”

What if I wanted to do both? use a custom subdomain and www at the same time. For example:

www.blog.example.com

Would I still get the 3 mentioned benefits of using “www” (CDN, DOS protection, etc.) while also being able to use the “blog” subdomain?

From my limited DNS experience, I don’t see how “www.blog.example.com” would be any different than “www.example.com”, but I don’t know what is happening on the github pages side of things and the documentation isn’t 100% clear.

Any clarification will be greatly appreciated!

Thanks

Edit: Also, for the CNAME file in the github repo is it suggested to put “blog.example.com” or “www.blog.example.com”? Are both equivalent? (assuming you have www CNAME setup on your DNS provider too).

To my understanding, for the purposes of the documentation, everything before .example.com can be considered the “subdomain”. Because of this, www.blog does not equal www and would not get all or possibly any of the mentioned benefits.

As for what to put in the CNAME file in the repository, you would put the fully-qualified domain name that you wished to use in the file. So if you choose to use [www.blog.example.com](http://www.blog.example.com), then you would put [www.blog.example.com](http://www.blog.example.com) in your CNAME file.

I hope that helps!

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