Should your blog be at blog.example.com or example.com/blog? We analyze all the evidence — and give you a clear recommendation.
The subdomain versus subfolder (subdirectory) debate is one of the most persistent questions in technical SEO. Every few years, a new study or Google employee statement reignites the argument. Entire companies have moved their blog from subdomain to subfolder — or vice versa — based on conflicting advice. What does the evidence actually say?
A subdomain places content before the domain: blog.example.com. A subfolder (subdirectory) places it after: example.com/blog. From a user perspective, both are accessible URLs. The difference is entirely in how browsers, servers, and search engines interpret the URL structure.
Google has made multiple statements on this topic, and they haven't been fully consistent. John Mueller, Google's Search Advocate, has stated on numerous occasions that Google treats subdomains and subfolders "the same way" and that there is no algorithmic penalty for using subdomains. He has explicitly said the choice doesn't matter to Google's crawler.
However, in a 2018 video, Mueller also said he would "personally" use subdirectories for most cases because it's "easier for Google to understand that this is all part of your website." This nuance suggests that while Google claims equal treatment, even their own engineers intuitively prefer the subfolder structure for content meant to be closely associated with the main domain.
The core SEO argument for subfolders is domain authority consolidation. When another website links to blog.example.com/my-great-post, does that link benefit example.com as fully as if the post were at example.com/blog/my-great-post?
The evidence suggests that subdomain links do "flow" PageRank and authority to the main domain, but potentially not as efficiently as subfolder links. Google's John Mueller has said links to subdomains do count for the main domain, but some SEO practitioners report observing that subfolder content ranks better because it more directly inherits the main domain's authority signals.
A notable real-world example: Moz moved their blog from blog.moz.com to moz.com/blog in 2014 and reported a significant ranking improvement. HubSpot similarly moved their blog to a subdirectory with positive results. These high-profile cases are frequently cited, though controlled experiments on large sites are methodologically difficult.
Despite the general preference for subfolders in SEO circles, there are legitimate reasons to use subdomains:
Different technology stacks: If your main site runs on a custom React application but your blog needs WordPress, putting the blog in a subfolder requires either serving WordPress at a path alias (complex) or serving both from the same server. A subdomain cleanly separates them with different web server configurations.
International sites: Country-specific subdomains (fr.example.com, de.example.com) can be useful, though Google's hreflang implementation works equally well for subfolders (example.com/fr/). Country-code TLD separate domains (example.fr) are often a better approach for genuinely separate markets.
Distinct products: When a company has truly distinct products or services that should rank independently (e.g., a developer tools company where docs.example.com is a separate documentation site), a subdomain makes organizational and technical sense.
Default recommendation: use subfolders. For most businesses adding a blog, help center, or content section to an existing website, example.com/blog over blog.example.com. The SEO benefit of consolidated domain authority is real and measurable in industry case studies, and the technical hurdles are manageable for most modern hosting setups.
Use subdomains when: Technical requirements genuinely require a separate server (different CMS, different tech stack, separate development team), for development/staging environments (always subdomain), for API endpoints, for distinct product verticals that should build their own domain authority independently, or for international/language-specific sites where geographic targeting matters.