It is known that a domain name has a certain structure and is divided into levels, which are separated from each other by dots. Levels are required for DNS * to function properly.
*DNS Is a technology that helps the browser to find the correct site by domain name.
Levels are counted from left to right. First comes the root domain (aka level zero) - this is the dot on the far right of the domain name. The common user does not see this point, but it exists at the DNS level. To make it clearer, this point is similar to “http://” before the site address - it is optional to enter it, the browser will substitute these letters by itself.
first level domain;
second level domain;
third level domain;
domain of the fourth level.
And there can be only 127 such levels, and each of them cannot contain more than 63 characters. The maximum length of a domain name with all subdomains must not exceed 255 characters. Sometimes, registrars may impose stricter restrictions.
Technically, each domain after the root is considered the domain of the previous one: .ua is a subdomain of the root domain, com.ua is a subdomain of the .ua domain, and ukraine.com.ua is a subdomain of com.ua. In practice, only domains of the third level and higher are called subdomains, and domains of the first two levels are called a domain name. This is done to make it easier to navigate, because there is only one domain name for the entire registration period, and there can be as many subdomains as you like.
Subdomains or subdomains are used to give an individual web page a unique name.
An address with a subdomain looks like a separate independent site. Besides, it is easier to remember than the text behind the slash in the link.
Each company project or individual service can have its own subdomain. Especially if each of them is designed for a different market or a different target audience. Google services are an example of this. The search engine is located on the main domain of the company, and all other services are located on subdomains: drive.google.com, mail.google.com, docs.google.com.
To distribute the load between the servers, each domain must be connected to the hosting separately - this will help to distribute the load among several servers. For example, the main site can be hosted on one server, and individual sections or secondary services on another.
Also, using a special program and code, you can redirect to a different IP address and separate directories
Internal services of the company can also be transferred to subdomains: a sub-site for company employees, a mail and FTP server, an environment for development and testing, and an image storage.
This will be convenient for those companies whose clients create accounts or sites, with their further publication on the Internet. For example, a company prints images on clothing and allows other users to create personal stores based on theirs.
Example: Wix or Tilda website builders - using these services, customers can publish sites and landing pages on their own subdomains. As a result, the address looks like this: example.wix.com or example.tilda.ws.
A subdomain can be created on the side of the DNS servers that use the domain. Most often, they belong to a domain registrar or hosting provider. In case you do not remember which DNS servers your domain is connected to, you can check this information in Whois.
Subdomains are perceived by search engines as independent sites. Therefore, for those who plan do site optimization, there are two things to consider:
External links to subdomains do not affect the authority of the main site. Under “authority” I mean the popularity of the site in the eyes of search engines. And inbound links are one of the factors by which it is calculated. The more links to your site there are on other sites, the higher its position in search results and, accordingly, the authority. It works on the following principle: since others link to a site, search engines believe that this site has useful content. If site pages are located on subdomains, links to them will not automatically affect the position of the main domain. With a small SEO budget, it is more profitable to use directories because all the authority from inbound links will be transferred to the main domain.
Each subdomain is ranked separately. Assuming the main domain ranks well for some queries, would that mean that the subdomain would rank well for them as well? – Answer “No”... The same rule applies and vice versa.
Therefore, it is better that the keywords on the main domain and subdomains are different. If they overlap, it will be more difficult to achieve high positions in the search results for the subdomain, and additional money will have to be spent on promotion.
Subdomains make sense if the keywords do not overlap. For example, pages with different products: okna.domain.ua, dveri.domain.ua, vorota.domain.ua.
This can be useful to someone who is doing SEO and technical analysis of the site. Perhaps some of the subdomains have duplicate content, but no one remembers its existence. Or your goal is to analyze your competitors' subdomains.
To find out all the domains indexed by the search engine, you need to enter a special query in Google. Just substitute your own or any other domain instead of "google.com".
site:google.com -inurl:https://google.com -inurl:https://www.google.com -inurl:http://google.com -inurl:http://www.google.com
There are also free services for finding subdomains: DNSdumpster or Pentest Tools. But they can't always find the right subdomain.
Also, you can check the subdomain using the special service Serpstat, on their website you can find subdomains of any domain.
To do this, enter the domain name in the search bar and go to the left menu in the section "Site Analysis" - "Domain Analysis" - "SEO Analysis" - "Subdomains".
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