The Question Almost Every Site Eventually Faces

You are about to launch a blog, help center, or shop. Should it live at blog.example.com (subdomain) or example.com/blog (subdirectory)? Both work. Both rank. But the choice affects ranking inheritance, technical complexity, and team workflow.

What Google Actually Says

Google's official line: subdomains and subdirectories can both rank well, and the choice is a matter of architecture preference, not SEO advantage. In practice, the picture is more nuanced.

Subdirectories inherit the domain's overall authority more directly. A new blog at example.com/blog starts with the topical relevance and link equity already built up at the apex. A new blog.example.com is treated as a separate site that needs to build its own signals β€” even though Google does pass some authority across subdomains.

When Subdirectories Are the Right Choice

  • The new section is closely related to your main site's topic.
  • You want it to benefit immediately from your domain's existing authority.
  • You can technically host it as part of the same site (same CMS, same template, same hostname).
  • You will not need to scale it independently or run on a different stack.

This covers most blogs, help centers, documentation sites, and content marketing efforts.

When Subdomains Are the Right Choice

  • Different stack required. Your main site is on Webflow but the docs need to be on Mintlify or GitBook β€” those tools cannot easily live at /docs.
  • Different team or company manages it. A community forum run by users, an acquired company's content kept separate, etc.
  • Different audience and topic. A SaaS company's investor relations site at investors.example.com, where mixing it with the main site would dilute both.
  • Geo-targeting. Some sites use ccTLDs as subdomains (uk.example.com) when ccTLD ownership is complex.

Common Migration Pattern

Many sites that launched on subdomains eventually migrate to subdirectories β€” especially blogs and help centers β€” because the SEO benefit is real and the technical cost (reverse proxy, CDN routing) has dropped over the years. The reverse migration (subdirectory to subdomain) is rare.

If you migrate, do it once and do it carefully:

  1. 301 redirect every old URL to the new one β€” not just the homepage.
  2. Update internal links to the new structure.
  3. Resubmit your sitemap in Search Console.
  4. Expect a 2–6 week dip in rankings as Google reprocesses the URL graph.

If your apex site has 500 referring domains and your blog at blog.example.com has 50, the blog ranks roughly like a site with 50 referring domains plus a partial bonus from the apex. If the blog were at example.com/blog, it would rank closer to a site with the full apex authority.

The exact multiplier varies, but for content that should benefit from your existing brand strength, subdirectories almost always win.

The Decision Rule

Default to subdirectories. Switch to subdomains only when you have a concrete technical or organizational reason that overrides the SEO advantage. "It feels cleaner" is not a reason β€” it is preference, and your future self running a single sitemap will thank you.