Subdomain vs Subfolder: What Google Says and Why It Matters

Few SEO debates have run as long as this one. Agencies have published case studies in both directions, people quote years-old Google statements at each other, and the argument usually ends with someone moving a blog from blog.example.com to example.com/blog/ and seeing traffic go up. Or not. I’ve seen both outcomes, and neither proves much on its own.

What Google says about subdomain vs subfolder

Google’s position has been consistent for years: its systems can deal with both, and there’s no general ranking preference for one structure. Google representatives have said repeatedly that you should pick whatever is easier to maintain. In the guidance on multi-regional sites, Google lists both subdomains (de.example.com) and subdirectories (example.com/de/) as legitimate structures and names practical pros and cons, not ranking ones.

That doesn’t mean the choice is neutral in practice. It means the differences come from what each structure tends to do to your site, not from Google scoring the URL pattern.

Where the structures actually differ

The internal linking row is where most of the real-world effect comes from. A blog in a subfolder tends to be woven into the site: product pages link to articles, articles link back. A blog on a subdomain, run by a different team on a different CMS, often gets a single link in the footer. Moving it into a subfolder often comes with fixing that, and the improvement gets credited to the URL change.

When a subfolder is the better choice

Use a subfolder when the section is part of the same project, run by the same people, and you can serve it from the same stack. That covers most blogs, help centres, landing pages and country versions of a shop.

For international sites, Google’s table names subfolders as easy to set up and low maintenance, with the downside that one server location serves all regions. With a CDN in front, that downside has mostly disappeared. Language folders plus hreflang is the setup I’d pick for most companies expanding beyond one country; the trade-offs against country domains are covered in country code vs .com.

When a subdomain is the better choice

A subdomain makes sense when the section is technically or organisationally separate:

• A hosted help desk or status page that only supports a CNAME
• A web application at app.example.com that has nothing to do with marketing pages and often shouldn’t be indexed at all
• A separate product with its own audience under one company brand
• Regional sites that need to run on servers in specific countries

In those cases, forcing a subfolder via a reverse proxy adds a moving part that can break. A subdomain with good internal links from the main site is fine.

Reverse proxy: a subfolder on a separate system

If the blog platform only offers a subdomain but you want the subfolder, a reverse proxy can mount it. In nginx:

location /blog/ {
    proxy_pass https://blog-origin.example.net/;
    proxy_set_header Host blog-origin.example.net;
    proxy_ssl_server_name on;
    proxy_set_header X-Forwarded-Proto $scheme;
}

The trailing slash on proxy_pass strips /blog/ before forwarding, so /blog/my-post/ is fetched as /my-post/ from the origin. The origin must generate links and canonical tags with https://example.com/blog/ as the base, or you end up with canonicals pointing at the origin hostname. That’s the step most setups get wrong.

The site reputation abuse problem

There’s one area where Google draws a sharp line, and it applies to both structures. The spam policy on site reputation abuse targets third-party content published on a host site mainly to profit from the host’s ranking signals. Coupon sections run by outside companies, “best casino” pages on unrelated sites, sponsored review collections: Google’s examples fit that pattern.

Putting such content on a subdomain doesn’t shield the main domain, and putting it in a subfolder doesn’t make it part of your site in Google’s eyes. If you’re tempted to rent out deals.example.com or example.com/coupons/ to a partner, that’s the question to ask first, not the URL format.

Should you move between them?

Moving a section from subdomain to subfolder, or the reverse, is a URL change like any other. Every old URL needs a 301 redirect to its new location, internal links and the sitemap need updating, and you should expect a few weeks of fluctuation. For moving between subdomains of different names, the Change of Address tool applies; for moves into a subfolder of the same domain it doesn’t, because Google doesn’t support path-level moves there.

If the section already ranks and is well linked, I wouldn’t move it for SEO reasons alone. If it’s an orphan on a subdomain nobody links to, fixing the links gets you most of the benefit without a migration.

Same question, different level

The subdomain question is a smaller version of the domain question. If the section is separate enough that you’re considering a different domain altogether, read domain SEO basics first. A brand-new domain starts from zero, while a subdomain or folder at least sits on the same registered name.

Planning a new project with its own name? Compare endings on the price list, see the .io domain page if it’s a tech product, or check whether the name is available before the structure discussion even starts.