Which are better for SEO – Subdomains or Subdirectories?

This week’s “Ask an SEO Expert” question is from Ursula Margolis who is a member of our Phoenix SEO and Internet Marketing Meetup.

Ask A SEO Expert - Subdomains vs Subdirectories

Thank you Ursula, great questions.

To begin answering your question I’m going to explain the differences between a subdomain and a subdirectory along with a few SEO tips.

Subdirectories vs SubdomainsWhat is a Subdomain?

If you have a website, technically you already have a subdomain.

As an example you can access Google’s website either of two ways:

  1. http://Google.com
  2. http://www.Google.com

Google.com is the top-level domain, and the default subdomain is www

You can replace the www with a different sub-domain, here is an example from Craig’s list.

  • Craigslist.com – The main website for Craig’s list
  • Cityname.Craigslist.com – The various cities

How Subdomains Get You in Trouble

Now as every website has a subdomain by default you should make the effort of configuring your site for the preferred domain otherwise you could be slapped with the dreaded duplicate content penalty by Google.

Let’s say your website has the top level domain of example.com and your home page is default.php.

If your site is NOT configured properly your home page could come with any of the following URL strings:

  • example.com
  • www.example.com
  • www.example.com/default.php
  • example.com/default.php

Then to make matters even worse your interior pages will also come up with similar variables,  “Duplicate Content HELL”.

How to Avoid Duplicate Content Penalty

To avoid the duplicate content penalty you tell Google and the other search engines which is the preferred domain/page for your content.

Here are 2 tips to avoid this dilemma

  1. Use Canonical Tags
  2. Create a .htaccess redirect

 What is a Subdirectory?

Think as subdirectories as folders under your top-level domain name.

An example is our website SEO Training SW

We list our SEO Training Classes in a folder called  /seo-training so the URL to this folder is http://www.seotrainingsw.com/seo-training/

Why Would I Want to Use Subdomains?

There are various reasons that you may want to use a subdomain on your site, the most common are:

  • Different Geographic Locations – Using Craig’s List again as an example, they use different subdomains for different regions
  • Various Product and/or Services – An example maybe that you have various product and/or services that you offer and you wish to separate these from your main site

Are Subdomains Considered Different Websites?

Yes, Google considers sub-domains completely different websites, therefore you should have:

  • Unique content
  • Unique XML Sitemap
  • Different Google Webmaster accounts

Does the Link Juice of the Top Level Domain Pass to Subdomains?

A common “Black Hat SEO” trick was to purchase a subdomain on a high page rank site as the link juice of the top-level domain did pass to the subdomain(s).

However this all changed back around 2011 with the Panda and subsequent Penguin update.

So today, no, you will get no “oomph” as link juice will not pass from the top level to the subdomain(s).

Which Are Better For SEO Subdomains or Subdirectories?

As you can see from this article there isn’t a one-size-fits all answer.

So here is quote from Matt Cutts of Google I think answers your question:

My personal preference on subdomains vs. subdirectories is that I usually prefer the convenience of subdirectories for most of my content. A subdomain can be useful to separate out content that is completely different. Google uses subdomains for distinct products such news.google.com or maps.google.com, for example. If you were a newer Webmaster or SEO, I’d recommend using subdirectories until you start to feel pretty confident with the architecture of your site. At that point, you’ll be better equipped to make the right decision for your own site.”

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Certified Master SEO Instructor by the Search Engine Academy and CEO and founder of SEO Training SW.
Roy Reyer
Roy Reyer
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12th February 2013 10 Comments

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