Stasia Avet
Mar 19, 2019 | 11 min read

Let’s say you have a website and want to separate a massive piece of content by putting it into a subdomain. Or maybe you’ve got a website with subdomains that you need to promote. In both cases, you’ve got to know what to do with your site SEO-wise because subdomain optimization is tricky.

In the next paragraphs, we’ll explain what subdomains are, why you might need them and how to promote them in a search.

What is a subdomain?

A subdomain is a subset of your website, serving to organize or divide your website content into distinct sections.

But how is it related to the domain?

A long, long time ago, back in the days of the ARPANET, domain names, as we know them today, did not exist. Instead, all directories in the network were marked with code numbers – IP addresses. That’s what you would’ve had to use in the 1970s to get to Instagram – 52.45.71.129, or Facebook – 69.171.234.21.

But in 1983, Paul Mockapetris invented the DNS concept – Domain Name System – that we are all still using to this day.

The main idea of DNS lies in its tree-like hierarchical structure: from the main domain to the subdomains.

The main domain is called the Top-Level Domain (TLD). Your unique website’s name would be the Second-Level Domain (SLD). A subdomain, in turn, is a third-level domain.

Take a look:

www-seranking-com-domain-structure

Regarding top-level domains – there are lots of them: .net, .org, .edu, .gov and regional ones: .it, .ru, .es, etc. Second-level domain is what makes your website’s address unique. And subdomains can have it any custom name: blog., help., store., online., etc.

If you already have a registered domain, you can create a subdomain for free, but you have to update your registration with the info that you’re creating a 3rd-level domain.

Let’s figure out when you’d need one.

Subdomain use cases

You need a subdomain if you have several types of content under the same domain, and, as a result, your users are puzzled and confused or the content pieces start getting in each other’s way in search results.

For example.

1. When you want to separate content by region

As a franchise business with offices in different countries or cities, you want to promote certain items or services in a specific area.

Subdomains will help you split local keywords and links for different regions so they don’t overlap and compete with each other.

It also can be useful for an informational website. For example, Craigslist.org has subdomains for each city it publishes ads for:Craigslist city subdomains

Or Wikipedia that shows content for each country on a specific subdomain:

Wikipedia's subdomains for regions

You can view subdomains for any domain with our
SEO/PPC Competitor Analysis tool

Google prefers websites having ccTLD – Country-Code Top-Level Domains – with each regional version being put on a separate domain:

Amazon's domains for different countries

But in order to do this, you need to buy each domain separately which can be quite expensive.

Before deciding on regional subdomains or country domains, you should consider all the pros and cons: what is easier to implement, what is less time-consuming to maintain, etc.

2. When you want to distinguish content based on its purpose

Some websites include various kind of information: product catalogue, blog, forum, knowledge base, members area for registered users, etc.

All these pieces of content may contain different information and can include varying functionalities and databases. In this case, subdomains are used to separate them from one another.

Look at the subdomains of WooCommerce – a customizable e-commerce platform for small and medium business:

WooCommerce themes subdomain
themes.woocommerce.com/ – examples and demos of the e-commerce site themes.
WooCommerce documentation subdomain
docs.woocommerce.com/ – guides, manuals, documentation, and tutorials for Woo’s products.
WooCommerce forum subdomain
ideas.woocommerce.com/ – forums.

You see that these subdomains have different both interface and purpose.

In the same way, you may need to segregate your help section (help.instagram.com), store (store.nytimes.com), blog (blog.hubspot.com), cloud service (online.seranking.com), etc.

Take a look at this list of the most popular subdomains to get an idea of why people create subdomains.

3. When you need to split product categories

It’s especially common for e-commerce websites or retailers to offer multiple categories of items for sale. For example, giant Chinese retailer AliExpress has several subdomain-levels, both for country and item categories:

AliExpress regional and category subdomains

The thing is that it’s easier to run a large website when it’s split into subdomains. Thus, subdomains can be managed by different people, with each team being responsible for a separate item category or region.

4. When you want to categorize a huge volume of content

Having subdomains for different product groups on e-commerce websites is similar to having 3rd-level domains for multiple content blocks on big media platforms.

For example, BuzzFeed has its main www subdomain, but also:

BuzzFeed's subdomains
As you can see, these content units are basically different projects under BuzzFeed’s umbrella. They target a different audience and have different purposes as well. And they definitely require separate managers who’ll be responsible for each of these subdivisions.

Tracking data on each one of them is much easier when they are split into subdomains.

5. When you have a mobile version of the website or an app

The mobile version of a website is basically a different website: it attracts different traffic using different acquisition channels. So one of the ways to satisfy the needs of mobile users and track all the needed data is to create an “m.” subdomain. Like m.hm.com, m.imdb.com, m.olx.com and many others. Keep in mind though that Google recommends using responsive design because it’s easier for developers to implement and maintain it, and doesn’t create extra difficulties for search engines.

You’ll also need a subdomain for brand apps, e.g. app.zeplin.io or app.sendgrid.comAnd for web versions of apps: web.whatsapp.com, web.skype.com, etc.

6. When you want to test new things on your website

One of the best things about subdomains is that you can use them for testing a new design or new CMS.

Testing a new CMS won’t influence the work of the main domain in any way. You can launch a new engine for your subdomain, test all of its features and learn how applicable it is to your website’s functionality. You can also tune the CMS to the special requirements of your hosting service. And only after having all tests done to your utter satisfaction you can move it to the main domain or to the entire website. During such tests, your website functions with no interruptions, generating traffic and revenue.

Test subdomains are usually secured by a password, so neither search engines nor users can access it. It’s also closed for the bots of the services that run website audits, which means you can’t use most automated audits to scan test subdomains.

In SE Ranking, though, you can give the bot permission to scan your closed domains. If you want to be sure everything works fine on your testing domain before you show it to the search engine, you can use our Website Audit.

To give the parser access to your test domains, enter your login and password into the parser settings:How to audit test subdomain

That way, you’ll catch things that might go wrong before Google spots any malfunctions.
Evidently, there are lots of cases when subdomains are the best way out. Now let’s sort out how search engines treat them, how subdomains affect rankings of the main domain and how to optimize them for better results.

Must-remember things about SEO for subdomains

Your subdomains and your domain are different websites.

It defines the whole SEO strategy for subdomains. Let’s sort it out step by step.

Webmaster settings for subdomains 

Уou need to register each one of your subdomains in webmaster panels separately. Here are Google’s instructions on how to submit website properties to the Search Console: https://support.google.com/webmasters/answer/34592?hl=en

Google Analytics will track the entire website, but you can set goals, filters, and get reports for your subdomains in particular. Read here: how to get data on your subdomain traffic.

Content strategy 

Identical texts on the domain and subdomain are duplicate content. No point in creating a subdomain if you don’t have enough unique content or if it doesn’t differ much from the one you have on the main domain.

To reduce common content duplicates (e.g. landing page presenting a product for different regions), use rel=”canonical” to show the prioritizing page. After creating a good new page on your subdomain, don’t forget to interlink it with your domain. And make sure you add it to the website’s sitemap so it gets indexed quicker.

Backlinks

You’ll have to build a link profile from scratch. Backlinks of the main domain don’t spread authority to subdomains. Besides, sometimes subdomains differ dramatically from the main domain (independent project, specific product type, etc.) which is why backlinks should also come from thematically different sources.

Tech nuances

  • You’ll need different robots.txt files for each subdomain. Keep in mind that your www. robots.txt file won’t be valid for any other subdomain or the main domain.
  • You’ll need separate XML maps.
  • Add the hreflang attribute for subdomains in different languages.
  • To make Google index your subdomains faster, make sure you are interlinking your main domain and subdomains. But don’t expect the domain to help subdomains to rank higher. The SEO for them are separate projects and would need to start from scratch. 

Tracking SEO results for subdomains

You can track your subdomains together with your main domain or separately. For example, in SE Ranking Keyword Rank Tracker you can choose either option the following way:

Tracking subdomains together with the main domain. When creating the project, go to the Advanced options and put a checkmark in the “Match subdomains” checkbox.How to check rankings of subdomains Thus, the service will take into account the pages of all your subdomains when calculating your SERP rankings.

Tracking each subdomain separately. For this, you need to create a separate project for each subdomain you want to monitor:

How to track subdomains separately

Enter the subdomain address into the “Website URL” field. Thus, the service will only check rankings for the given subdomain and its subdomains (4th level and further), e.g. it.website.com, support.it.website.com, blog.it.website.com, etc.

Can subdomains harm your website’s SEO?

Google’s John Muller claims that the engine knows how closely subdomains and their domain are bounded. But technically they are different websites. Take the websites created as subdomains for .wordpress.org. It answers the question, whether a subdomain can harm your domain’s SEO. The answer is ‘no’ if you are playing fair.

However, if you have malware subdomains, Google can label the whole domain as malicious.

Also, If you try to push your subdomains/domain in search for the same queries, Google can penalize your domain.

The worst case scenario is when you find indexed subdomains (that you were unaware of) with duplicate content or the test ones – those are really harmful and they are hard to find.  

Final thoughts

Don’t create subdomains without a good reason.

Decide why you need them, what is a goal for creating them and how you are going to achieve them.

If you are an SEO master and got a website with subdomains to work on, analyze why they were created in the first place. Do they work well? Do they meet their initial purpose? Do they need to be more efficient?

Again, make sure you hide all the technical subdomains or those containing confidential information from the search engines.

And if you have a large enough workforce to maintain subdomains, go for it.

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35 comments
  1. Hey, Stasia!

    Thanks for putting this together – I had some doubts about subdomains and duplicate content before. Now it’s much more clear!

    Keep up the good work!

    1. Aggrey, I really appreciate your feedback! If you have any questions on the topic, don’t hesitate to ask 🙂

  2. wonderful. I was always confused by this, but the examples were really illustrative. I also appreciate the final thoughts. Exactly what I was looking for!

  3. We use HubSpot to create and host our landing pages and forms. These exist on a subdomain. go.ourcompanyname.com/ Although these pages are not content-rich the do get a fair amount of traffic and clicks and conversions. Since they are separately hosted is our main domain missing out on SEO advantages? And if so is there anything we can do to tie the advantage back to the main domain?

    1. Hello Tamera! Thanks for the question. Well, it depends on how close and well-connected is your content on your main domain and the subdomain. If on your subdomain you have completely different information that has nothing to do with your domain, there won’t be any particular effect for the domain. But if, for example, you have a blog on your subdomain and it’s ranking well – your main domain also can get a boost.
      In general, don’t worry about missing out on some SEO advantages. If your subdomain gets traffic and conversions – it’s great for your brand, for your product in general.

  4. Hi!Thanks for all the info! My sub-domain is hosted on Shopify on which I’m selling products. My main domain is hosted on a completely different server. The “2” websites are about the same thing/product, but on the main domain I only have a few buy buttons (through embedded code from my shopify store). I did it this way, because Shopify’s themes are limited in regards to making look books etc, which I can be much more creative with when using a non-shopify theme etc. I have noticed however, that when I do a search for my brand name, only pictures from the main domain show up, plus all kinds of other domains, but not the sub domain hosted through Shopify. Here and there I can find one. Is this the case where my subdomain is hurting my SEO efforts, and am I better to do it all on 1 domain? I have the 2 sites separately verified with google search console, etc. I hope you can answer this. Thank you!

    1. Hello Anna! Thank you very much for your comment!

      You wrote that your websites are about the same product. But do they actually differ?
      Google tends not to show similar websites owned by one person in the SERP. So it may even be better for you to keep only one of them.

      But if your websites differ in any way (e.g. target different audience, offer extra services, sell different products, etc) you should emphasize these differences. Google needs a good reason to display both of your websites in the SERP.

  5. Hi
    I have a domain X.com without any content. The domain has three links of three subdomains targeting different business. I am facing crawling issues on two subdomains. What do you think is the real issue here.

    1. Hello Aamir. Crawling issues can occur for many reasons, and it’s hard to say what’s exactly the problem in your case without knowing any technical details. The best advice, for now, would be to check your website for technical errors, page indexing problems, duplicate content, etc.

  6. I have checked the domains from every angle , no duplicate content as such. i also analysed the server log files of all 3 subdomains which showed bots crawling important pages less frequently.Here is the main domain
    https://altaresh.com/
    and three subdomains can be found on it as links. Please advise what could be the reason

    1. There can be multiple reasons for that. The best strategy is still the same: sort out the pages with crawling issues (check their status in a Coverage report tab in the GSC, use Fetch as Google tool), examine their tech condition, and remember that it’s ok if the bot doesn’t come to visit all your pages daily (it doesn’t have to). What is known for sure is that the very existence of subdomains couldn’t cause the crawling problems.

    1. Thank you for your question, Sandeep!
      Before moving sections of the site to separate subdomains, you need to understand how exactly it will benefit you.
      From an SEO standpoint, the general practice is to avoid such changes since every reorganization like this takes time for a search engine to notice and interpret it properly. And there is always a chance that something will be misunderstood or that you can make technical mistakes during the transfer.
      Meaning, if there’s no definite real need to do this, it’s better not to.

  7. Hi I have several websites that i want to create subdomains for. The goal being that each subdomain is for a different city. So when someone searches “pizza near me” in Hollywood, the subdomain Hollywood.mypizzasite.com comes up even though we are not physically located in Hollywood. Each site would have identical content. Would this improve local SEO and would that subdomain come up in the search query mentioned.

    On that same note, would a subdomain for each city, pointing to the main domain have the same SEO affect as a subdomain with an actual clone of the main site with content actually on subdomain site. Thanks.

    1. Thanks for the questions, Johnny!
      Well, just adding a regional subdomain itself (in your case it’s a city subdomain) won’t help you get to the SERP’s top for local keywords. The power of this strategy lies in the developing of regional subdomains — adapting content and getting local links. Besides, take a look at the SERP results for your keyword — if there are only local companies that have an actual address in your target region, it will be hard to compete with them.
      If you don’t change the content on your city subdomains at all, but just clone the main site, then most probably the main domain will be the one to get ranked. It has more authority links and the search engines trust it more.
      The query “pizza near me” means that the user is looking for an actual pizza place nearby. If you are not present in the same region, you won’t satisfy this query. Probably, you should focus on the delivery queries, if you provide such a service.

    1. Hello Albina, thanks for your question! The right way to link a localized subdomain – the way it’s comfortable for your users.

      In a footer or a header of your site, you need to add a button for selecting a language. It should be clearly visible so that people who do not speak the language of the main domain could easily change it.

      Besides, it’s important to redirect users to the corresponding page upon switching the language. For example, I’m reading an “About us” page in English but want to read it in Spanish, so when changing the language I should be redirected to the ES version of “About us”, not to the home page of the subdomain.

      Also, don’t forget about the proper use of the href lang tag – so search engines know for which region and language a particular page is targeted.

  8. Hi Stasia,

    Thank you for an insightful article. I would be very thankful for your advice.

    If my current domain is hosting an eCommerce store listing the products targeting the retail consumers, and now I want to target institutions for bulk orders with separate content regarding the services aspects and blogs, I believe I should host my new content on a subdomain instead of on a subfolder. The objective is to achieve good SEO results to engage my institutional target groups.

    Thanks in advance.

    1. Hello Max,

      Thank you for your kind words! I really appreciate it.

      Regarding your question, you should bear in mind that having a subdomain doesn’t benefit your SEO by itself.
      A subdomain is basically a different website. So think of it this way: do you have enough reasons for creating a separate website for wholesaling? If you plan to have multiple site sections, big product categories, a purchase procedure different from the one on your main domain, a different set of services – yes, it’s better to move your wholesale options to a subdomain.

      If you have just a couple of bulk options to offer and the process of purchasing is the same as on your main domain, if it’s just a “little extra” to your basic range of services, then I believe there is no strong need for creating a subdomain for it.

      Hope it will help. Good luck!

  9. Hi Stasia,

    Thank you so much for clarifying my doubts in such a nice and clear manner.

    My sincere thanks and appreciation for your wonderful blog.

  10. Hi Stasia,
    Great article! I wanted to ask you – If I want to build 10 websites for 10 different clients from the same niche (Sports Instructors), If I use a subdomain for each client, for example: client-name.domain-name.com
    will it affects SEO for each client?

    1. Thanks for you feedback and question, Meir! If you cannot create a separate website for each client, you can create subdomains for each client. They will be seen as 10 separate websites by Google. However, from the point of view of branding, doing so isn’t a good idea, but everything really depends on your main domain, the client websites, the content they publish, and the SEO promotional strategy used.

  11. Hi Stasia,

    I would like to know if having my forum hosted by Tribe.so on a subdomain would hurt the SEO on my main domain. My main domain has a blog, setup as it should. I love Tribe.so’s features, but not sure if having the forum on a subdomain will help or hinder SEO overall. The forum’s purpose is to create sub-groups and offer exclusive content, how-to articles and general customer support as well as a good ol’ general discussion. Thanks for your help!

    1. Good question, Alex! From the technical perspective, these are different websites. If you don’t spam the main domain with links and stick to Google’s rules, your websites should be fine.

    1. Subdomains are neither good nor bad for SEO, Michael. They are just one of the ways you can create and maintain a website. This method has its pros and cons, and depending on your goals and needs, you can determine whether or not you need to use subdomains on your site.

  12. Hi,
    I have created a free site in wordpress.com like xyz.wordpress.com Now I want this site to do seo for google ranking. Is it possible? If possible and i do so, can google penalize me? How much safe, fair, wise to do seo?

    1. Thank you for reaching out, Shohid! To answer your question, yes, you can promote and do SEO for your free website created in WordPress. SEO is an ongoing process that requires you to constantly optimize your site for search engines and human visitors in order to aqcuire organic traffic. So, it’s safe, fair, and wise to do SEO for your own or a client’s website as long as you adhere to Google’s guidelines and carefully study our blog. That way, your chances of getting penalized by the search giant will be minimum. Like Google, we at SE Ranking also recommend you hire or reach out to an SEO expert for help.

  13. Hi Stasia / Andrew,
    Thank you for your post and for taking time to answer all the questions in the comments.
    Here’s my case: I have online jewellery shop and I’m planning to attach a wordpress blog to it. my ecommerce platform provider has a feature to host a blog on subfolder, however, it’s simplified version of wordpress blog with very limited plugins. Also, for some reason in address bar it has http instead of https (all other pages have https). When I spoke to them, they said that I could have third party blog on subdomain address.
    Would you advise to have the blog as subdomain – it’s going to be more like lifestyle blog with the spice of jewellery, posts including travel, tutorials, cooking, giveaways and competitions, history etc. and interlinked with main domain/shop.
    Also, do you think if the the blog on subdomain achieves high DA (domain authority), it will drag the main domain’s (where shop resides) DA up? I have checked my competitors’ DA for the shop and blog (which they have on subdomain) and they showed same numbers.

    1. Thanks for your feedback and question, David!
      In your case, having your blog on a subdomain wouldn’t be the wise thing to do. You should think of your blog as a separate website that requires time and resources to be optimized and promoted in search. Moreover, it’s evident that your ecommerce platform provider is offering you an incompetent solution for your blog. It is recommended that you create your blog as a subfolder on the main domain.
      As for the second part of your question, since you will be directly linking out to the main domain, the subdomain will have an impact on its DA.
      Hope this helps and answers your question, David!

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