Can anyone explain why one is better than the other, and in what circumstances? Things I'm considering: SEO consequences (if any), scaling issues (if any) and anything else I'm not thinking about.

Facebook, for example, uses subdirectories for profile pages. Tumblr uses subdomains. Are there specific reasons why?

Another consideration: domain mapping.

Hope the question isn't too general, but I haven't found a clear answer.



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Here's the snippet from the 101 that answers your question:

Subdomains vs Subfolders

A subdomain install means that your sites will look like this:

  • Main site:
  • Sub Site #1:
  • Sub Site #2:

A subfolder install means your sites will look like this:

In addition, if you use a subfolder install, the post URLs on your main site will have the slug /blog/ prepended to them, causing them to look like this:
At this time, you cannot customize that slug, nor easily remove it.

There is no SEO benefit at this time to using subdomains or subfolders, and you can map a domain name to either install, so the decision is purely cosmetic. See http://www.mattcutts.com/blog/subdomains-and-subdirectories/ for an explanation

The Domain Mapping subject is extensively covered, so I'm pretty sure that the 101 reading will answer this and many other questions you may have.

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  • 1
    Scaling really isn't an issue either. The only gotcha I've run into is when someone on the main site made a page with the same name as a subsite on a subfolder install. Easy enough to fix, and caused much giggles. - My general thought is 'If all the sites are 'the same' then it's subfoldrs, if they all look different, subdomains.'
    – Ipstenu
    Jun 3 '12 at 15:24
  • Here we go, the gap I left in the answer filled by the half-elf support rogue herself, thanks @Ipstenu !
    – brasofilo
    Jun 3 '12 at 20:05

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