The subdomain vs subfolder question is about where a section of a site lives: on a separate hostname such as docs.example.com, or under a path on the main domain such as example.com/docs. Google has said its systems can handle either. In practice, subfolders tend to be simpler to manage as one site, while subdomains suit sections that are technically or organizationally separate.
What Google has said
Google representatives have said repeatedly that it does not treat subdomains as inherently worse, and that it works out which parts of a domain belong together. Google does not publish exactly how signals are shared between hosts, so claims that one choice is always better for rankings go beyond what is documented.
Practical differences
A subdomain is a separate host to crawlers: it has its own robots.txt, may need its own Search Console property, and often runs on a different platform. A subfolder shares the main site's robots.txt, navigation, internal links and analytics setup, which makes it easier to link sections together and see them as one site.
- Subfolder: one robots.txt, one sitemap index, shared navigation, simpler reporting
- Subdomain: independent hosting and deploys, separate crawl settings, clearer team ownership
- Subfolder with a reverse proxy: separate platform served under the main domain's path
Choosing for a SaaS site
Content meant to support the marketing site, such as the blog, guides, glossary and comparison pages, is usually easiest to run in subfolders. The logged-in app, status page and sometimes docs live on subdomains because they are separate products. If a hosted platform only supports subdomains, a reverse proxy can serve it under a path, at the cost of extra setup.
Example
Moving a blog into a subfolder
Hollowmere, a data privacy SaaS, runs its blog at blog.hollowmere.example on a hosted CMS with its own navigation, which rarely links to product pages. The team proxies it to hollowmere.example/blog, adds the main nav, and 301-redirects every old subdomain URL. The point of the move is shared navigation and simpler reporting, not a guaranteed ranking change.
Common mistakes
Moving without redirects
Changing hostnames is a site migration. Every old URL needs a 301 to its new path, or links and indexing history are lost.
Forgetting the subdomain's robots.txt
Each subdomain serves its own robots.txt. A leftover Disallow: / on docs or help subdomains is a common surprise.
Questions
Not according to Google's public statements. Many SEOs prefer subfolders for practical reasons, but a well-linked subdomain can perform well. Treat any certainty either way with caution.
