Is it really time to ditch subdomains for a single website?

Why does Google advocate for a consolidated single site?

The logic is straightforward: each subdomain is treated by Google as a separate entity. Specifically, blog.example.com and shop.example.com do not optimally transfer their domain authority.

When you fragment your web presence into multiple subdomains, you dilute trust signals. The backlinks pointing to blog.example.com do not directly boost shop.example.com. The crawl budget gets split, and visibility disperses.

What does Mueller mean by 'very different target audience' exactly?

Mueller does not precisely define this critical threshold. We typically refer to major geographical segmentations (fr.example.com vs us.example.com) or radically opposed business verticals (recruitment vs consumer e-commerce).

The boundary remains vague. A blog and an online shop do not necessarily constitute 'very different' audiences. However, a B2B site and a B2C site from the same group may justify the separation.

What is the actual impact on PageRank and authority?

In a subdirectory structure (example.com/blog/, example.com/shop/), all trust signals converge to the root domain. Link juice flows naturally through internal linking.

With subdomains, you must build the authority of each entity separately. Links between subdomains are treated as regular external links, without any special bonus. You end up managing multiple distinct sites, each starting from scratch in terms of credibility.

• Authority consolidation: a single domain centralizes all trust signals and maximizes the impact of backlinks.
• Crawl efficiency: Google allocates a crawl budget per domain, not per subdomain—fragmentation reduces overall efficiency.
• Technical simplicity: managing a single site avoids configuration duplication, cross-domain canonical issues, and SSL complications.
• Legitimate exception: distinct geographical markets with localized content, different languages, specific regulations.
• False good idea: creating thematic subdomains to 'better organize' when categories would suffice.

Is this recommendation consistent with field observations?

Absolutely. SEO audits of sites that have migrated from subdomains to subdirectories regularly show measurable visibility gains within 3-6 months. Consolidation boosts pages that were stagnating.

I have seen corporate blogs on blog.brand.com stagnate for years. Migrating to brand.com/blog/ allows articles to start ranking for competitive queries they never touched before. The main domain lends them its accumulated credibility.

What nuances should be added to this generic advice?

Mueller remains deliberately vague about the threshold of 'very different audience.' [To be verified] in each specific context. A multi-brand site with totally distinct brand identities may justify the separation, even if the audience partially overlaps.

Technical constraints also play a role. If your blog runs on a stack incompatible with your main site, forcing integration may create more problems than it solves. Sometimes, it’s better to accept a loss of authority than to break technical reliability.

In what cases does this rule really not apply?

Complex web applications (SaaS tools, platforms) often benefit from a dedicated subdomain for reasons of performance, security, and separation of concerns. app.example.com vs www.example.com makes sense if one is a marketing front and the other is software.

High-traffic sites may also justify fragmentation for infrastructure reasons. Managing 10 million pages on a single domain poses technical challenges that some organizations prefer to avoid through distribution.

What should you do if you are currently using subdomains?

Start with an honest architecture audit. List all your active subdomains and assess whether each truly serves a distinct audience or if it’s just a historical habit.

For each subdomain candidate for migration, measure its current organic traffic, backlink profile, and ranking on key queries. You will need these baseline metrics to measure the post-migration impact.

How to migrate without losing existing traffic?

The migration from subdomain to subdirectory follows the same rules as a classic domain migration. Permanent 301 redirects, URL-by-URL mapping, increased monitoring for 3-6 months.

Notify Google via Search Console: declare the address change if possible, submit sitemaps of the new directory, and ensure Googlebot follows the redirects. Never touch the old URLs until traffic has stabilized on the new ones.

What mistakes should you absolutely avoid during the transition?

The classic mistake: redirecting the entire subdomain to the homepage of the main domain. Every URL from blog.example.com/article-xyz must point to example.com/blog/article-xyz, not to example.com. Avoid chain redirects as well.

Another frequent pitfall: forgetting to migrate technical configurations. Your canonical tags, sitemaps, structured data, your robots.txt—all must be adapted to the new architecture. A canonical that still points to the old subdomain after migration creates confusion.

• Map all URLs of subdomains to migrate, without exception.
• Implement permanent 301 redirects URL by URL, never in bulk to the homepage.
• Update all internal links to point directly to the new URLs.
• Ensure that the internal linking of the main domain naturally incorporates the new sections.
• Monitor Google Search Console daily during the first month: 4xx errors, indexing coverage, performance.
• Keep redirects active for at least 12 months, ideally indefinitely.