Subdomains vs. Subdirectories – What Should I Know About Subdomains and SEO?

This post is meant to be helpful for those with an intermediate level understanding of SEO. If you have a basic understanding of how Google and other search engines rank pages and are aware of some basic SEO best practices but aren’t yet an SEO expert, we think you’ll find this post useful. You can also find DIYSEO posts classified by level of expertise on the following pages:

One SEO question we’re frequently asked is where to have new sections of a site “live”. For instance you might be adding a forum so that you can better serve your customers and people looking to learn more about your company. Since there will be a lot of useful content there about your product and your niche, you want to have all of the posts that your staff and your customers and potential prospects make show up in search engines. You’re presented with three potential options:

  • Use a third party solution and have the forum live on their site. This might make things pretty turnkey and easier for you. To get to the forum, people would type in the URL
  • Have the forum live on a subdomain of your site – this means that the forum will live on a special section of your domain. The URL would look like
  • Have the forum live in a subdirectory of your site – this means that the forum will live off of the main section of your domain. The URL would look like

So what’s the best place to “put” your forum for SEO?

The answer is generally (but not always) a subdirectory. The reason for this is that often times the forum content people are creating for you will attract links. Content that gets links helps tell Google that that entire site is trustworthy. If you host your content on another site then any links you get are telling Google that their site is trusted, so that option isn’t ideal.

Towards the same end, a subdirectory is generally acknowledged to generate more trust or “link equity” for your main domain than a subdomain. This is a similar premise: by putting your forum on the root domain you’re telling the search engine that this content is closely aligned with your main domain, and in turn the engines generally assign slightly higher weight to the transfer of equity from a subdirectory to the main domain than to the transfer of equity from a subdomain to the main domain.

This said, if you have specific reasons for your business to choose one of these options over another, you might want to opt for a less SEO friendly option. If you’re trying to determine what the difference between the tactics you can use the following mental model as a way to “grade” the options from an SEO perspective (NOTE: this is a very rough estimate meant to be directionally useful):

  • Other Domain: 50
  • Subdomain: 90
  • Subdirectory: 100

So choose the option that has the best combination of SEO and general business benefit for you.

Categories: SEO Questions

  • Tom

    Thanks for the info. I’m just about to merge one of my websites and a forum and was just looking for some info on this.

  • IQ

    Very interesting read.

    I’m curious, from a SEO perspective is it better for me to put say a job board in a root domain instead of subdirectory – or as far as SEO is concerned both are the same since it’s the same domain.

    The reason is I am starting a new site which will initially have a job board as the main product. Later I may add a social media forum, wiki page, etc.. So my question is in order to build trust should I start off with the Root Domain and later add subdirectories and let my job board act as the main interface / page

    OR should I start up inititialy with putting the job board in a subdirectory ( knowing that currently is empty and only points to the jobs subdirectory. Is this better practice since this will allow me in the future to build a proper integrated interface on the root domain or am I missing out on SEO tactics?

    Thank you for all your assistance and I really appreciate your help with this small dilemma.


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  • Tyler

    Given your analysis, what was the rational for installing this blog as a subdomain of vs. a subdirectory? Blogs are far more common than forums and sites frequently install them to get more content and links to their domain, so I’m curious what the pro-arguments are for a subdomain blog. Thanks!

    • DIYSEO Team

      Hi Tyler,

      Great point and not mentioning this in the post is an omission on our part :) – this is a good example of when functionality can somewhat trump the advantage of having a blog or subsection of your site live off the root. The blog is a sub-domain here mainly because the DIYSEO blog is WordPress whereas the rest of the site uses a custom CMS and integrates closely with our Web app, so putting the blog in a subdirectory (while doable) would have presented some technical issues that we didn’t feel out-weighted the marginal SEO benefit. I’d imagine this is the impetus for a lot of blogs/forums/etc. that opt for a subdomain, and again it’s a general business decision so you have to weigh factors like the difficulty of maintaining your site if you have something live off the root, whether you want to really establish a subdomain as a different part of your site, etc. versus the SEO benefit.

      Great catch Tyler and thanks for the comment!

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