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Subdomains: What Are Those & When To Use Them?

When it comes to subdomains, It’s easy to confuse the name with the obvious. Though, they are filled with specific characteristics that make them unique members of the Internet ecosystem.  You may feel confident about this topic. Though, there is always room for improvement. A common question among many is “what is a subdomain?”. And we are going to answer this question.

What Is a Subdomain?

A common question among many is “what is a subdomain?” & “what is it used for?”  In simple terms, a subdomain is a subdivision of a larger domain. It allows web developers to organize their existing websites into individual sites. Many developers make use of a subdomain if their content is different from all other pages on their websites. For those who don’t know, subdomains are displayed by their sections to the left of the URL.

To get a better understanding of the concept of subdomains, it’s essential to dissect a domain name from top to bottom. Before learning the rest, it’s wise to understand the subdomain definition fully. A complete domain name would include a Top-Level Domain (TLD) followed by a second-level domain or SLD. For example, the TLD is the part of a domain that is displayed after the last dot is indicated. As an SLD makes sure a domain name is unique on your website.

representation of what is a domain and what is a subdomain

When browsing the internet, you will commonly find the World Wide Web (WWW) at the start of a URL. The good news is, it doesn’t always have to be used at the start of a URL. In fact, you can use any word in the English language to create a subdomain. Meaning, you won’t have to be burdened with purchasing a new domain name. 

How to Use Subdomains

A subdomain is a segment of a website, but it is also viewed as a separate website by the search engines. Think of it as slicing a pizza with different toppings of each side, while you see it as a whole pizza, your friend may see it as two separate pizzas. The same can be said when it comes to learning how to use subdomains and the way they are used on the internet. 

While developers recognize the way subdomains are presented, they make use of them to organize and arrange their websites. This enables developers to control the way pieces of their websites are indexed. Google-based companies take advantage of subdomains for a large number of purposes. The primary reason is to provide a webpage with a unique specification from the rest of the website while maintaining the same domain name. Read on to view some real-life examples.

Creating a Separate Web Page for Mobile-Usage

Making use of a subdomain can deliver a mobile phone version of a website to visitors. Google and other search engine operators detect whether one is using a tablet or mobile phone. Smartphone and tablet users will be shown mobile-friendly versions of websites - providing a better experience among users. Thus, developers provide mobile versions of their websites that cater to mobile-phone users and considering screen-size.

Mobile-friendliness is necessary for today’s market. Most people surf the internet through their hand-held devices, compared with laptops or desktops.

desktop, tablet and mobile adaptive web pages

When Creating a New Website

A common practice of making use of subdomains is to treat them like a testing ground. In terms of developing a new or existing version of a website. You can install applications like WordPress to a subdomain, and take advantage of it as a separate entity from the main domain. Web-masters have the ability to integrate a performance analysis, which checks for updates and plugins on their subdomains prior to publishing to the live website.

When subdomains are used as a testing ground, the word chosen for the subdomain wouldn’t be a normal keyword one would think of searching for on Google. Because the content is something you don’t want your users viewing as of now. This is known as “hidden” pages, where developers are able to create and test updates without them becoming live. It’s almost like having an area 51 on your own domain!

Make User-Friendly Web Pages

Depending on the occasion, the content may need to cater for different website visitors. If your website is aimed at those in another country, it is necessary to translate your content into the local language of that nation - the same applies to visitors from multiple countries. If this is the case for your website, you can create subdomains that enable visitors to view your content in their own language. 

  • A simpler and less costly approach towards this is to add separate subdomains in multiple languages, rather than having a bilingual or multilingual website.

subdomains of one domains made for users from different countries

In some cases, web developers might require modifying their content for other regions of the same country. For example, Craigslist displays separate domains for different regions of the US. Each subdomain caters for the region its aimed at. Though, separate web pages exist under the same master domain name.

Differentiate Your Blog from the Main Website

For bloggers or those who have a company blog, consider placing it under a subdomain. Blogs with high amounts of traffic can make the website slow-down in terms of speed. Meaning, turning your blog into another entity under the same domain solves this issue. This can also be used for redesigning your blog or changing the blog to a different CMS. 

differentiating blog from the website

All in all, it’s a good idea to place your blog onto a subdomain. As it has a different purpose from the rest of your website. 

Differences Between Subdomain and Subdirectory

You know the reasons why subdomains are used among web-developers. It’s wise to also learn the differences between subdomains and subdirectories. Read on to take a look at the subdomain vs. subdirectory comparison by viewing the pros and cons.

difference between subdomain and subdirecroty

Pros and Cons of Subdomains

Due to a variety of reasons, the use of subdomain has decreased over the last few years among developers. There are both advantages and disadvantages to subdomains. Take a look:


  1. Subdomains act as different web pages on root-domains. Google, Bing, DuckDuckGo, Yahoo and others display subdomains as unique and unrelated to their main domains. The type of URL informs search engines to recognize subdomains almost as separate websites. 
  2. Separate web pages on subdomains equal to additional results in search returns. If your primary domain and subdomain(s) have high search positions, you’re decreasing the chance for any competitors to gain traffic. As well as allowing potential visitors to have easier access to your website.
  3. You can use SEO keywords in your subdomain’s URL to boost your chances of gaining traffic. Additionally, clarifying the main purpose of your website.


  1. Your marketing strategy becomes diluted by potential visitors connecting your product with unrelated products in their minds. You sell weight-loss products, but wish to market golf equipment. Main supermarkets also offer this. Thus, potential customers may associate your product with the main chains. 
  2. Your URL may be too long for users. Though, this depends on the domain and subdomain names.
  3. Subdomains may not be recognized as legitimate sites by people surfing the internet. You may be under the assumption that Google rankings are full of subdomains, internal web pages and blog posts makes a difference to the opinion of potential clients. Though, it may not.

Pros and Cons of Subdirectories

Prior to observing the pros and cons of subdirectories, it’s wise to understand the subdirectory definition. So, “What is a subdirectory?”. It is a subdivision of an active website which is included at the end of a URL. For example, In other words, the division strategy hosts a subdivision from a domain. It becomes more commonly used among developers for multiple purposes; SEO, technical considerations, hosting limitations, etc.


  1. Subdirectories enable websites to maintain their main purposes. A far simpler approach to differentiating your website is to optimize a web page with subdirectories, instead of numerous subdomains under the same domain name.
  2. Transitioning visitors to other web pages can be more effective and simpler through making use of subdirectories. For example, visitors are reading your blog, and can easily navigate to your ‘about me’ page. Meaning, the experience is more positive for the user.
  3. Modifying or moving your code to another location is far easier within a subdirectory. In most cases, website code placed under the filing systems. 
  4. For developers who have made use of subdirectories, finding and tracking analytics are far more efficient. As content is stored in the same place, under the domain. Meaning, Google Analytics recognizes all of your subdirectories as one website, meaning all data stored into a fixed location online. 


  1. Subdirectories cannot allow developers to aim content at different regions, or create multi-language versions as easily. However, subdomains allow you to do this. 
  2. Google may avoid displaying some of your subdirectories if they are placed within your website.
  3. Using multiple subdirectories may make a URL look stretched out or uncoordinated.

How to Find Subdomains

Business analysts, security engineers, pentesters and other specialists are facing such tasks as finding subdomains of a domain. You might be curious, why would they need to do that?  

Some white hat hackers use subdomain tricks to stir up security threats which can be damaging for companies or small startups. A recent incident involved Vine, where a hacker had made the code publicly available for download through hacking one of their subdomains. 

The fastest and easiest way to find subdomains is to use online tools like Findsubdomains. This tool can be used by specialists from across various IT sub-sectors & technological fields to perform different analytical scans like viewing the infrastructure of an organization(s), identifying security gaps and weaknesses, etc. Pentesters can use this tool to find technical domains that are open to the public, check the endpoints for vulnerability. This is just the small part of functionality this tool has, so why don’t you try it yourself?

Final Thoughts

You may be thinking “Which form of division is right for me?”. The greatest advice we are able to provide is to review the pros and cons of both subdomains and subdirectories to see which is right for you. Another tip is to speak to a professional to get the answer you’re looking for. However, it’s wise to keep in mind that having an insecure subdomain may be dangerous.