Subdomain vs Subfolder for SEO: What Google Says and When to Use Each

The subdomain vs subfolder SEO debate comes back every time a company launches a blog, a store, a help center or a new language. Google's own position is relaxed: asked about it in 2018, John Mueller of Google answered "In general, we see these the same", while adding that he "would personally try to keep things together as much as possible" (Search Engine Journal, May 2018). This guide explains what changes in practice, case by case.

What is the difference between a subdomain and a subfolder?

Both are ways to organize a section of a website, at two different levels of the URL:

• A subdomain sits before the main domain: blog.example.com, shop.example.com, fr.example.com. It is created in the DNS and can point to a different server or platform.
• A subfolder (or subdirectory) sits after the domain: example.com/blog, example.com/shop, example.com/fr. It lives on the same host as the rest of the site.

What does Google say about subdomains and subfolders?

Google has never announced a ranking penalty for subdomains, and its public statements point the same way: both structures can rank. Three official facts matter more than opinions.

A subdomain is a separate site for crawling

Google's crawl budget documentation states that "Google's crawling infrastructure defines a site as a unique hostname", and gives the example of two subdomains of the same domain that are treated as separate sites with separate crawl budgets. For most sites this is neutral; for a site with hundreds of thousands of pages, it changes how crawling is shared.

Search Console can group them, or not

According to Search Console Help, a Domain property "aggregates data for all subdomains, protocols, and subpaths" and is verified through DNS, while a URL-prefix property only includes URLs that start with the exact prefix. With a Domain property, blog.example.com and example.com appear in the same reports; with URL-prefix properties, you need one per subdomain.

Google advises keeping things together

John Mueller's 2018 advice, as reported by Search Engine Journal: keep related content together as much as possible, and use a subdomain when the content is truly different from the rest of the site. Google's explanation of how search engines work also shows why: Google has to understand that two hostnames belong to the same entity, and links are its main clue.

Why do subfolders often perform better in practice?

Google may "see these the same", but the mechanics of SEO favor the subfolder in most situations:

1. Signals add up on one site. A backlink earned by a blog post in example.com/blog benefits a domain whose product pages sit one click away. On a subdomain, that domain authority flows to the main site only through the links you add between the two.
2. Internal linking is natural. Same navigation, same templates, same footer: articles and commercial pages link to each other without effort.
3. One site to maintain. One robots.txt, one sitemap index, one crawl to audit, one set of Core Web Vitals.
4. A clearer brand. Users, journalists and AI assistants see a single domain name behind every page they cite.

Many published case studies describe traffic gains after moving a blog from a subdomain to a subfolder. They are encouraging but anecdotal: a migration often comes with other improvements, so the gain cannot be attributed to the URL structure alone. Our guide to domain authority explains how these third-party scores are calculated and why they are not a Google metric.

When does a subdomain make sense?

A subdomain is the right choice when keeping the content in a subfolder would be technically difficult or would mix two different products.

Software companies are the typical example: the marketing site, the blog and the documentation belong in subfolders, while the product itself lives on app.example.com. Our page on SEO and GEO for SaaS companies details this split.

Mistakes to avoid with subdomains

• Forgetting that www is a subdomain. www.example.com and example.com are two hostnames: pick one, redirect the other with a 301 and keep canonicals consistent.
• Leaving a staging subdomain open. An indexable copy of the site creates duplicate content; protect it with a password.
• Using one robots.txt for everything. Each hostname reads its own robots.txt file, so a rule on example.com does not apply to blog.example.com.
• Isolating the subdomain. Without links from the main navigation, a subdomain behaves like a new site that has to earn its visibility from zero.
• Splitting analytics. Configure your analytics tool to follow visitors across hostnames, or conversions from the blog will look like lost traffic.

Blog, languages, store: which structure for each?

The blog

A subfolder, almost always. The blog is where you earn links and answer the questions your buyers ask; you want that authority on the domain that sells. If your blog runs on a separate CMS, a reverse proxy can serve it under example.com/blog without moving the platform. On WordPress, the blog sits in a subfolder by default (see our WordPress SEO and GEO guide).

Languages and countries

Google's guide to managing multi-regional sites compares the options. Subdirectories are "easy to set up" and "low maintenance (same host)"; subdomains are also easy to set up, allow "different server locations" and make separation of sites easier. URL parameters are not recommended. For most companies, example.com/fr/ with hreflang tags is the simplest structure to run. Our international SEO guide covers the full choice, including country domains.

The store

If your e-commerce platform can run on the main domain, use subfolders for categories and products. If it imposes a subdomain, accept it and compensate with strong cross-linking: links from the blog to categories, from the home page to the store, and a consistent header across both.

How do you move a subdomain to a subfolder without losing traffic?

Moving blog.example.com to example.com/blog is a migration in its own right. Follow the same discipline as any SEO migration:

1. Inventory every URL of the subdomain, with traffic and backlinks.
2. Map each old URL to its new one, one to one, without sending everything to the blog home.
3. Set up 301 redirects at the subdomain level, with no chains.
4. Update internal links, canonicals, hreflang and sitemaps so they point directly to the new URLs.
5. Check the redirects with a redirect checker on a sample of old URLs, including the ones with backlinks.
6. Monitor in a Domain property of Search Console, which shows both hostnames side by side during the transition.

Expect a few weeks of fluctuation. A drop that lasts usually points to missing redirects or lost content.

Subdomains, subfolders and AI visibility

ChatGPT, Gemini and Perplexity cite URLs, and the hostname is part of what readers see in the citation. When your guides live in a subfolder, every citation displays your main domain and reinforces the brand that sells. On a subdomain, the same citation can look like a separate site. Whatever the structure, the same rules apply as in classic SEO: crawlable pages, links between sections, and authority built over time. A domain authority tracker shows how that authority evolves, and Sorank's backlink acquisition obtains natural backlinks automatically from its network of 5,000+ users.

Subdomain or subfolder: the decision

Choose a subfolder by default, and a subdomain only for a separate product, platform or audience. If you already run a subdomain that works, link it tightly to the main site before considering a migration. Then put your energy where rankings are decided: content and links. Sorank publishes optimized articles directly in your blog subfolder on autopilot, with internal links to the pages that sell.