Should you really overlook PageRank when deciding between a domain and a subdomain?

Why does Google emphasize user logic so much?

Takeaki Kanaya's statement cuts through a persistent belief in the SEO community: the idea that a subdomain would receive less “link juice” than a subdirectory. Google claims that this technical consideration should never guide architectural choices.

The central argument: user experience comes first. If a service, product, or editorial line justifies a distinct identity, the subdomain is legitimate. Conversely, if everything fits within a thematic continuity, the subdirectory is more coherent. Google's algorithms adapt — not the other way around.

Does this position really change the game on the ground?

Google implicitly acknowledges that subdomains can exceed their root domain. This is an important admission: each subdomain thus possesses actual autonomy in the index, with its own ranking potential.

Specifically? A well-optimized subdomain, targeting a specific niche with quality content and dedicated backlinks, can outperform a diluted generalist main domain. This aligns with what we observe in giants like Amazon (aws.amazon.com) or Reddit (old.reddit.com).

What does this imply for internal linking and backlinks?

If Google treats domains and subdomains with such algorithmic autonomy, it means that linking between the two is not strictly perceived as internal. A link from the root domain to a subdomain likely counts more than a simple traditional internal navigation link.

External backlinks pointing to a subdomain directly benefit that subdomain, without necessarily “flowing up” to the root domain through a cascade of PageRank. This creates a clear segmentation in the index.

• Never structure domain/subdomain solely to optimize PageRank distribution
• Prioritize editorial coherence and logical architecture for the user
• Accept that a well-managed subdomain can become more visible than the main domain
• Treat the linking between domain and subdomain as semi-external links, not pure internal linking
• Consider backlinks to a subdomain as assets specific to that subdomain

Is this statement consistent with ground observations?

Yes and no. On large sites, it is indeed observed that some subdomains take on an independent life (forums, marketplaces, knowledge bases). But asserting that the choice between domain and subdomain has no SEO impact is an oversimplification.

In practice, a subdirectory immediately benefits from the historical authority of the root domain, its accumulated backlinks, and established crawl budget. A subdomain often starts from scratch or almost — even if Google can transfer some trust. [To verify]: what degree of “reputation transfer” exists between root and subdomain? Google remains vague on this.

What nuances should be added to this recommendation?

Google speaks of an ideal: not letting the technique dictate the architecture. However, in the real world, technical constraints (different stack, separate team, need for isolation) and SEO constraints (domain history, crawl budget, thematic dilution) must coexist.

A classic example: a marketplace launched in a subdomain (marketplace.site.com) to isolate potentially toxic UGC content. Here, the choice is not purely “user logic” — it's also about SEO risk management. And that is legitimate.

Another nuance: claiming that a subdomain can “surpass” the main domain is true, but it often requires a massive investment in content, backlinks, and optimizations. This is not automatic or free.

In what situations does this rule not fully apply?

When a site has a history of penalties or quality issues on the root domain, starting a strategic project on a clean subdomain can be a valid defensive strategy. Google suggests not to think in terms of PageRank, but if the root is toxic, a new subdomain can protect a new project.

Another limitation: on small sites with little authority, creating a subdomain for a blog or an e-commerce section often just dilutes an already fragile authority even more. In this case, concentrating everything under one roof (subdirectory) remains more effective in the short term.

What actions should you take to choose between a domain and a subdomain?

First, ask yourself about the editorial and functional coherence. Is the content or service being considered a natural extension of the main site, or a distinct universe with its own positioning? If it is distinct (marketplace, forum, SaaS application), then the subdomain is defendable.

Next, assess the available resources. A subdomain requires specific investment: dedicated content, its own backlinks, independent technical optimizations. If you do not have the means to support this subdomain in the long term, it’s better to stick with a subdirectory.

What mistakes should be avoided in this decision?

Never create a subdomain solely to “isolate” weak or duplicated content in the hope of protecting your main domain. Google eventually associates the two entities if they share a clear identity (same owner, same Search Console, same patterns). Segmentation is not an invisibility cloak.

Also, avoid multiplying subdomains without a clear logic. Each new subdomain fragments your overall authority and complicates your link architecture. Three active and well-maintained subdomains are worth more than ten ghost subdomains.

How can you check if your current architecture is optimal?

Audit the distribution of organic traffic between your root domain and your subdomains. If a subdomain stagnates despite efforts, consider whether regrouping it into a subdirectory would be more effective. Also analyze the behavior of external backlinks: are they pointing heavily towards the root or towards the subdomains?

Check the coherence of your internal linking between domain and subdomain. If you treat these links as purely classic internal links, you may be underestimating their real value. Google perceives them as semi-external — so make sure to take care of them.

• Assess editorial coherence: does the content justify a distinct identity?
• Measure the resources available to support a subdomain long-term
• Audit the current distribution of traffic between root and subdomains
• Analyze the backlink profile: where do quality external links point?
• Ensure that linking between domain and subdomain is strategic, not automatic
• Never multiply subdomains without a clear functional reason