Is SEO effective? Differences, advantages and disadvantages between subdomain and subdirectory



  • What is the difference between a subdomain and a subdirectory?
    Which one is better for SEO?

    If you are reading this article, you probably have similar questions.

    Subdomains and subdirectories are both elements that make up a URL, but many people do not clearly know the difference between the two.

    Understanding the difference between the two will help you create the correct URL when describing your site, optimizing your SEO results.

    In this article, we will explain the difference between subdomains and subdirectories, and the SEO effects of subdomains and subdirectories.

    If you are planning to open a new site, please refer to it.

    What is URL/domain?

    In order to understand subdomains and subdirectories, we will first explain the terms URL and domain.

    The meaning of each is as follows.

    Difference between URL and domain


    Abbreviation for Uniform Resource Locator.
    Something that shows the location and information of a website or file on the Internet.


    A single element that makes up a URL.
    There are different types of domains such as top-level domains, second-level domains, and third-level domains.

    There are various elements that make up a URL, including subdomains and subdirectories.

    We will explain the difference between subdomains and subdirectories in the next chapter.

    Difference between subdomain and subdirectory

    Subdomain and subdirectory are similar URL-related terms, but they are actually completely different concepts.

    Subdomains and subdirectories




    sub domain

    Subdividing a domain and using it as a completely different domain

    Blue text is subdomain


    Something that creates and uses a hierarchy for each theme in the same domain

    Subdirectories are in red

    Subdomains and subdirectories are both related to URLs, but the major difference is whether they are used as separate domains or under the same domain.

    Which is better for SEO: subdomains or subdirectories?

    Google has made it clear that using subdomains and subdirectories will not affect your rankings.

    Are there any benefits to using subfolders or subdomains?

    Choose the method that makes organization and management the easiest for you. There is no particular impact on index registration or ranking.

    Quote source:Frequently asked questions: Google Search crawling and indexing | Google Search Central

    This simply means that the difference between a subdomain and a subdirectory has no advantage or disadvantage in search rankings.

    However, since the reputation of this domain affects both subdirectories and subdomains, it is important to strengthen the domain.

    Also, just because the difference in domain does not affect SEO, do not set a random domain.

    Users also read information from domains, so be sure to set a domain that is easy for users to understand and that does not deviate from the site theme.

    Advantages and disadvantages of subdomains and subdirectories

    Subdomains and subdirectories each have their own advantages and disadvantages.

    Subdomains and subdirectories




    sub domain

    ・Costs can be reduced

    ・The evaluation of this domain also affects subdomains.

    ・If the evaluation of this domain is low, there may be negative effects.


    ・Backlinks directly affect this domain

    ・Increase the number of indexes

    ・Does not become an independent domain

    I will explain each.

    Advantages of subdomains

    The biggest advantage of subdomains is that they reduce costs.

    It costs money to acquire a new domain, but you don’t have to pay for a subdomain.

    Another benefit is that the reputation of the main domain affects subdomains.

    Although this domain and subdomain are treated as separate sites, the evaluation of this domain will affect the subdomain.

    However, you cannot expect any direct effects from linking from a subdomain to this domain.

    On the other hand, backlinks from subdomains may affect the main domain.

    This is because Google Search Console treats subdomains as internal links of the main domain.

    Disadvantages of subdomains

    The disadvantage of subdomains is that if the reputation of the main domain is low, it may have a negative impact on the subdomain as well.

    This means that subdomains are influenced by the main domain, for better or worse.

    If the reputation of this domain is low, we recommend that you acquire a new domain instead of a subdomain, develop it to some extent, and then switch to a subdomain.

    Advantages of subdirectories

    The two advantages of subdirectories are that backlinks directly affect the domain and that you can increase the number of indexes.

    Since subdirectories exist within this domain, links from external sites to subdirectories are treated as backlinks of this domain.

    Also, since it exists within this domain, if the content increases in the subdirectories, the number of indexes can be increased in this domain.

    The number of indexes is also an important factor for SEO, so subdirectories have an advantage over subdomains in this respect.

    Disadvantages of subdirectories

    On the other hand, the disadvantage of subdirectories is that the range of content that can be published is limited.

    Since subdirectories exist within this domain, there is no point in publishing them unless the content is in line with the theme of the site.

    For example, it would feel strange if a marketing-themed site had content like recommended izakaya in Tokyo.

    In SEO, the expertise of the information is also linked to evaluation, so if you publish content that is significantly different from the site theme, your evaluation may drop.

    How to use subdomains and subdirectories

    You don’t have to think about the different uses of subdomains and subdirectories.

    Please use the following criteria to ensure proper site management.

    How to use subdomains and subdirectories




    When choosing a subdomain

    When dealing with different themes for the same trademark or brand

    When a marketing company conducts a supplement business

    When selecting subdirectories

    When a specific theme can be grouped under the same trademark or brand

    When a supplement company publishes a column about supplements

    As mentioned above, companies such as Yahoo and Apple also use subdomains and subdirectories.

    Basically, they are used according to the above criteria, so please be sure to pay attention to this point when surfing the Internet.

    How to configure cross-domain settings in Google Analytics

    If you choose a subdomain, you will need to configure cross-domain settings in Google Analytics.

    Since a subdomain is a separate domain from the main domain, if you do not perform cross-domain settings when measuring with Google Analytics, users across domains may not be recognized as the same user.

    This time, I will introduce how to configure cross-domain settings in Google Analytics4.

    1. Open Google Analytics4 and select GA4 properties.
    2. Click “Data Stream” and select the target stream.
    3. Click “Advanced tagging settings”.
    4. Click “Domain settings”.
    5. Click “Add condition”.
    6. Register the domain you want to set and click the [Save] button.

    *Match type can be selected from “Exact match”, “Contains”, “Match at beginning”, etc., but basically “Contains”

    You can configure cross-domain settings using this procedure.

    Universal Analytics, which was the mainstream until now, will no longer be available, so if you want to set up a new one from now on, set it up with Google Analytics 4.

    Summary: Understand the characteristics and operate the site correctly

    Subdomain and subdirectory are similar words, but they are actually very different concepts.

    As introduced this time, domains have no effect on SEO.

    However, indirect effects may differ.

    It’s not a good idea to choose a domain with too much SEO in mind, but please choose a domain based on the criteria for correct usage that I introduced this time.

    In order to get the correct evaluation from search engines, first decide on the theme of your site and choose a domain.

    Choosing the right domain will help you run your website correctly.