It’s partly a misconception today, but it was accurate historically, and the honest answer is that Google’s treatment has evolved without becoming a clean binary. Historically, Google’s systems evaluated subdomains somewhat independently for authority and ranking purposes, treating a subdomain more like its own site than a section of the root domain. Google has since confirmed, through statements from John Mueller and through product features like Search Console’s domain-level property, that its systems increasingly evaluate certain signals at the registrable-domain level, which spans subdomains. But subdomains can still be crawled, indexed, and can still rank somewhat independently depending on how genuinely separated the content on them actually is. It depends on the specific site and signals involved, not a rule that applies identically everywhere.
The mechanism: what actually changed and what didn’t
The historical treatment made practical sense: blog.example.com and shop.example.com could, in principle, be run by completely different teams, on different infrastructure, with entirely different content, and nothing about the DNS-level relationship between a subdomain and its root domain guarantees they share the same quality, ownership intent, or topical focus. Treating them with some independence was a reasonable default for a system trying to assess site quality and relevance without assuming subdomains are always tightly coupled to their root domain in practice.
What’s changed is that Google’s systems have gotten better at recognizing when a subdomain functions as a genuine, integrated part of the same overall site, rather than as an operationally distinct entity. The clearest public evidence of this shift is a product decision: Search Console’s domain-level property type aggregates data across all subdomains and protocols under one registrable domain by default, which only makes sense as a default if Google’s own systems generally treat that domain, subdomains included, as one cohesive unit for most purposes most of the time. Mueller has made comments over the years consistent with this: for many typical setups, the practical difference between putting content on a subdomain versus a subfolder of the root domain has narrowed, because Google’s understanding of domain-level relationships has improved.
Why “it depends” is the honest answer, not a dodge
The nuance that keeps this from being a clean “subdomains are now identical to subfolders” statement is that the underlying content and infrastructure separation still matters. A subdomain that’s genuinely operated as an extension of the main site, same team, same general quality bar, cross-linked naturally, content that clearly relates to the main site’s subject matter, tends to benefit from and contribute to the root domain’s overall standing much like a subfolder would. A subdomain that’s operationally and topically distinct, a support portal with a completely different content type and quality level, a separate product line with its own audience and purpose, or infrastructure run by an entirely different team with different standards, can still be evaluated with meaningfully more independence, simply because the signals genuinely differ from the root domain’s.
This is consistent with how Google’s ranking systems generally work: they’re trying to assess actual site quality and relevance, and a subdomain’s DNS relationship to a root domain doesn’t override real differences in content, purpose, or quality that exist between them. The subdomain-versus-subfolder question was never really about the technical DNS structure itself; it was always a proxy for whether the two pieces of content genuinely belong to the same coherent site experience.
Worked example: the same subdomain, two different outcomes
Consider a company running support.example.com in two different configurations. In the first configuration, the support subdomain is built on the same content management system as the main site, uses the same header, footer, and navigation, links naturally to and from product pages on the root domain, and covers troubleshooting content that directly extends the products described on the main site. Editorial standards match the rest of the site. In this configuration, there’s little reason to expect Google’s systems to treat this subdomain as meaningfully separate from the root domain; the signals a quality or relevance system would look at, content focus, internal linking patterns, apparent ownership and maintenance, all point toward one coherent site.
In the second configuration, the same support.example.com hostname is run by a third-party vendor on a completely different platform (a help-desk SaaS product with its own templates), has no cross-linking with the main site beyond a single link in the footer, uses different branding conventions, and covers generic troubleshooting content that isn’t really specific to the company’s own products. Here, even though the DNS relationship is identical to the first scenario, subdomain and root domain sharing a registrable domain, the actual signals available to Google’s systems look like two different operations. There’s no principled reason to expect the same “it’s basically one site” treatment, because the underlying reality genuinely isn’t one site in any meaningful sense beyond the shared hostname suffix.
This is the practical test worth applying before assuming Search Console’s domain-level aggregation implies uniform treatment: ask whether an outside observer looking only at the content, linking, and apparent maintenance patterns, with no knowledge of the DNS structure, would conclude these are parts of the same site. If yes, expect subdomain-versus-subfolder to matter little. If no, expect Google’s systems to keep evaluating them with real independence regardless of the domain-level reporting default in Search Console.
An edge case worth naming: multi-brand and franchise structures
A structure that complicates this further is the multi-brand or franchise subdomain pattern, where a parent company operates brandname.example.com for dozens of distinct local franchises or sub-brands, each with different owners, different content quality levels, and only nominal affiliation with the root domain’s brand. This is a case where treating all those subdomains as one cohesive entity would actually be the wrong outcome for a quality-assessment system to reach, since the individual franchise pages can vary enormously in quality and relevance even though they share a root domain. Google’s systems evaluating this kind of structure with meaningful independence between subdomains isn’t evidence that “subdomains are still separate entities” as a general rule; it’s evidence that the assessment is tracking the real underlying variation in ownership and quality, which is exactly what a system built around genuine site-quality assessment should do.
What to avoid assuming
Don’t treat this as settled into a universal rule in either direction. It’s inaccurate to say subdomains are always evaluated as entirely separate (that’s the outdated historical framing), and it’s equally inaccurate to say Google now treats all subdomains identically to subfolders in every case (Google has never made that absolute claim; the actual public statements consistently include qualifiers like “generally” and “in most cases” rather than an unconditional rule).
Practical implication
When deciding whether to launch new content on a subdomain or a subfolder of an existing site, the deciding factor should be how integrated the new content genuinely is with the existing site’s purpose and quality standards, not an assumption about which structure Google favors by default. If the content is a natural extension of the same overall site and audience, a subfolder or a well-integrated subdomain will likely behave similarly under Google’s current, more domain-level-aware evaluation. If the content is operationally and topically distinct enough that it genuinely functions as a different site, expect Google’s systems to continue evaluating it with real independence, regardless of which subdomain-versus-subfolder choice was made, because that independence reflects genuine differences in the content, not just the URL structure chosen to host it.
