A few days ago, I conducted a major experiment on my site. Before then, I had major sections of the site categorized as domains. For example:
http://pictures.example.com/whatever http://help.example.com/whatever http://internalstuff.example.com/whatever http://tips.example.com/whatever
Now I converted most of the domains into one so that accessing the same resources is as follows:
http://example.com/pictures/whatever http://example.com/help/whatever http://example.com/tips/whatever http://internalstuff.example.com/whatever
I left one subdomain alone because its strictly meant to be used for assets but I'm wondering if that is even a good idea anymore because I have my site currently setup to load pictures after the HTML loads, not while the HTML loads.
After converting 6 subdomains into one domain using the method above, and running mobile tests with webpagetest.org, it turns out the time to first byte significantly decreased from 210ms to about 135ms.
So my question is, with such a large image site like mine, Am I better off to just run everything off of only one domain and hope for the lowest time to first byte, or should I keep my assets running off of a subdomain?
I'm just trying to figure out if there is really any kind of advantage to using a subdomain.
And as a side note, since the merge, my income at least doubled on average.