When I help a new customer, it’s always interesting to get a first impression. For example, manually checking the site, scanning the GSC reports, checking third-party visibility tools, triggering an initial crawl of the site, etc. And with large and complex sites, you just never know what you’re going to find.
Two recent audits revealed something I’ve seen several times over the years. And it’s a situation that can be obscured when companies have no idea it’s even happening. After a quick scan of each website, I reached out to both customers with a quick question.
“How long have these subdomains been active and are they necessary?”
And her reaction was interesting.
“Wait, which subdomains??”
They didn’t know the subdomains were active, some of the subdomains contained content, and each had different levels of search visibility. So yes, people found these subdomains through search.
Of course, it’s important to understand all areas of a website that are active, how they are handled, whether they rank in the SERPs, whether they contain malware or other security issues, and how users interact with that content.
Quality assessment at hostname level:
When it comes to quality, I’ve discussed many times how Google has stated that all indexed pages are taken into account in the quality rating. However, it is also important to understand that Google’s quality algorithms work at the site level (often) at the hostname level. I covered this in my post about site-wide signals and Google’s site-level rating and impact. This is why you often see subdomains affected differently when major algorithm updates are rolled out.
Here’s a tweet covering a comment from Google’s Gary Illyes about algorithms like Panda that operate at the hostname level.
For example, here are three subdomains of the same website that were affected differently during the major core update in September 2022. One rises, but two fall sharply:
Security issues can pose a serious problem (for organic AND ads):
Another concern is security, hacked content, malware, etc. You definitely want to know if a fraudulent subdomain is hacked, contains malware, or has security issues. And although most focus on the organic effects, it can also impact ADD. I wrote a case study I heard about this happening to a major client of mine a few years ago. Due to their technical configuration, many fraudulent subdomains were created and some were affected by malware. And when that happened, their Google ads were blocked.
After this introduction, you are probably wondering how to find the subdomains that are active on your website. Below I’ll describe some quick methods to understand which hostnames are active, whether they’re ranking in the SERPs, and more. Note that there are also some developer tools you can use to delve into subdomains. However, below I will focus on common SEO tools and tactics. Again, you might be surprised at what you find.
GSC crawling statistics (via domain property):
Setting up a domain property can provide several key benefits. One of them is the ability to view data across all subdomains and protocols. To clarify, you definitely don’t want a domain property to be set up without other properties, but it’s important to include them.
If you check the crawl statistics reports in GSC while accessing the domain property, you will see all subdomains (or what Google calls child domains) listed on the home screen. This can be an eye-opening experience for some larger and complex websites. And if you find that multiple subdomains are active, you may want to add them as properties to GSC to get a complete overview of the SEO operations there.
Site Explorer in Bing Webmaster Tools:
I know a lot of people forget about Bing Webmaster Tools, but it contains a lot of good information from another major search engine. And Site Explorer is a great way to find all the subdomains that Bing knows about. You will see them listed on the left side of the Site Explorer and can view individual pages for more information.
Subdomain search visibility (rankings) via third-party tools:
If you don’t know all the subdomains on your website, using third-party tools can help. By checking your domain’s search visibility with tools like SEMrush, ahrefs, and Sistrix, you can see if subdomains are ranking in the SERPs. Each of the tools I mentioned in the coverage pops up subdomains.
When subdomains are listed, they are not only active, but they actually rank in search results. And that means users may interact with the content there. From a content perspective, if you have old content ranking on a subdomain, it’s probably not a big problem. However, if it is hacked content full of spam sites, you should act quickly to take action.
After entering a domain in SEMrush, you can access the subdomains in the organic research report.
In Sistrix you can access the hostname reports:
And in ahrefs, you can view the Site Structure report to see a breakdown of all areas of the domain with search visibility.
Creative Website Inquiries:
Ah, the good old site query. Fast, dirty and versatile. You can find all subdomains on a website other than www via a creative website query. For example, here is a site query for google.com that returns subdomains other than www. And on top of that, you can start adding negative site queries to drill down even further. I’ve been doing this for years on the major sites I help. Here, too, some interesting insights can emerge.
site:google.com -inurl:www
site:google.com -site:developers.google.com
Bonus for smaller sites that are worried about this. It’s always smart to call your hosting provider:
If you don’t have a development team to fall back on, definitely call your hosting provider. You can pretty quickly drill down and identify subdomains that are active on the site. They can also help you turn them off quickly if necessary.
Summary: Don’t let your subdomains surprise you.
It only takes a few minutes to calm your mind. Follow the steps above to check your subdomains. And for larger and complex websites, you might be surprised at what you find. It’s just another example of the SEO iceberg. What matters is what lies beneath the surface. And subdomains fall into this category. Good luck.
GG