In my previous post, I jumped to conclusions a bit too quickly. Let me explain the problem in more depth.
A long time ago, there was a study on coupon sites discussing real-world examples of whether it’s better to choose a subdomain or a subfolder.
Over 250 high-authority sites hosting coupons were analyzed. There was a news site, and coupons were added on top of it. Thanks to the main domain’s authority, the coupon section quickly ranked at the top. Or failed to do so)
The full table with the sites is here.
Back in 2019, Google announced it would crack down on subfolders and subdomains if they differed significantly from the main site.
https://twitter.com/googlesearchc/status/1161725709926182912 :
“We’ve been asked if third parties can host content in subdomains or subfolders of another domain. It’s not against our guidelines. But as the practice grows, our systems are improving to better understand when such content is independent of the main site and treat it accordingly.”
In other words, Google has a clear stance: if the site is NOT similar to the main site, trust is not passed on.
And this leads to the following conclusion: perhaps it’s not about subfolders themselves, but about how similar the two sites are to each other.
https://guru.wildberries.ru/ and https://www.wildberries.ru/ differ from each other, according to Google
Whereas, for example, https://www.ozon.ru/club/ and ozon.ru do not. To me, they both look similar, though still not exact copies.
Another example: the subdomain discountcode.dailymail.co.uk is no different from the main site dailymail.co.uk, and its menu even includes links to other sections, and the site ranks well. But there are also examples where both sites barely resemble each other and yet rank at the top in Google. Example: coupons.cnn.com
You can research this yourself. Below is a list of such sites.
List of high-traffic coupon sites on subdomains, about 50 in total.
On subfolders, also about 50.
Paste them into Ahrefs Batch Analysis and see for yourself.
As we can see, both options rank. The difference may lie in how Google perceives the coupon site—as part of the main site or not.
Therefore, at the moment, I don’t have a definitive conclusion on which approach is better. If a subdomain doesn’t differ in design and code, Google might consider it part of the main site and pass authority to it.