The most common mistake made by many webmasters is not knowing the real effect of starting subdirectories or sub-domains. So what is the difference between sub-domain and sub-directories in terms of search engine optimization? To be clear, let us just take a look at the structural differences between sub-domains and subdirectories:
Many common blogging networks offer sub-domains instead sub-directories. For example, typepad.com, blogspot.com, wordpress.com, etc. The moment a new sub-domain is created, it is similar to a new domain from the search engine’s perception. We need to implement all the basic steps we applied for any other new website to the new sub-domains. If you create a blog in blogspot.com, you will start off with a page rank of 0 or unavailable for the sub-domain (example.blogspot.com). Blogspot.com itself has high page rank but it won’t pass any page rank value to sub-domains so you won’t get a single bit of PR juice for your sub-domain created in blogspot.com or wordpress.com. Because your newly created sub-domain is essentially at ground-zero in terms of back links and is treated like a new domain, we need to build our back links like we would with any other new site.
Similarly, you don’t immediately get page rank value for new sub-directories. New sub-directories need to wait for the next page rank update to get decent page rank. The only difference now, is that the page rank value from main domain will pass PR juice to any newly created sub-directory. If Blogspot.com allowed you to create a blog with sub-directories, then you would probably enjoy higher page rank without building any back links to your sub-directory. The same applies to any other domain – if you struggle hard for years to build a reputation for a domain and plan to branch out your business, then sub-directories will give almost immediate page strength to your new business branch. Now, we know why many blogging platforms give sub-domains to new bloggers instead sub-directories.
However, both sub-directory and sub-domain plays a role in online industry. If you are planning to give away a free website, then offering it as a sub-domain is the best way to protect your business. Other than that, I don’t really see the benefits of using sub-domains. Even for country specific sites, we can use a sub-directory; i.e. atniz.com/us/ to support US clients and declare this sub-directory to support US traffic in Google Webmaster tools. They accept sub-directories to assign for country specific (local search engine) optimization ranking purposes. Similarly, you can add sub-directories to language based sites. You don’t have to use sub-domains to support different languages on your site. Almost 90% of the reason to start sub-domains can be answered using sub-directories and enjoy almost immediate high ranking benefits. Why should we start from zero level if we already have a good spot in authority and ranking?
However, some business owners prefer to start fresh for a whole new market or product. Thus, they prefer to use sub-domains instead of sub-directories. Probably, multiple reasons like language, product availability, etc force one to use a sub-domain. They don’t mind building their company reputation in a new business niche or country from ground zero level. This might be the style of the owner or webmaster that manages their company domain. Basically, we need to build some back links to our new service even if it is on sub-directory. We need to apply the same SEO strategies to sub-domains, but target more niche or country-specific links. Possibly, the webmaster doesn’t want to mix and run multiple countries or business niche under one umbrella. Some may even get country specific domain names like .co.uk, .com.my, .co.in, etc to represent each office or business in local country.
In simple words, sub-domains can give more unique presence compared to sub-directories. If our main business domains have exists in the market for 2 years with a complete search engine optimization campaign running for each month, then a new sub-domain will be 2 years behind while, sub-directories have saved that 2 years of SEO campaigns and enjoy some benefits almost immediately due to the existing domain authority. Although, sub-directories are much easier to get ranked and attract converting traffic when compared to sub-domains, some businesses prefers to keep their brand name unique and have a presence in all business niches or countries they provide services in. Either way, most top SEO consultants and marketing agencies will suggest using a sub-directory first to help them acquire good ranking more quickly. Now, we know the benefits of using a sub-directory over a sub-domain.
Share you experience using sub-domains and sub-directories. Where we can use sub-domains?