The decision to host a section of your site at a subdomain (blog.example.com) vs a subdirectory (example.com/blog) used to be more contested than it is now. The current consensus among SEO practitioners is clearer, but it's worth understanding both why the consensus exists and where the edge cases still matter.

The honest framing: subdirectories are usually the right choice for most cases. Subdomains have specific use cases where they make sense. The default should be subdirectory.

The historical context

For a long time, Google treated subdomains and subdirectories as roughly equivalent. Some practitioners argued that subdomains were treated as separate sites (with separate reputation and ranking), while subdirectories inherited the parent domain's reputation.

Google's stated position evolved: subdomains and subdirectories are both valid; the choice is based on what makes sense for your site, not on SEO advantage.

The practical observation: subdomain content sometimes does get treated differently from main-domain content in ways that don't always favor the subdomain. The mechanism isn't fully transparent but the pattern is consistent enough that most SEO practitioners now default to subdirectories.

Why subdirectories tend to win

Reputation transfer: the main domain's reputation transfers to subdirectories more reliably than to subdomains. A new subdomain often starts with less ranking power than a subdirectory at the same age would have.

Crawl budget: search engines allocate crawl budget per domain. Content on a subdomain shares crawl budget with the parent, but the subdomain still has its own crawl priority signals. Subdirectories are unambiguously part of the parent.

Link equity: external links to subdirectory content directly strengthen the main domain. Links to subdomain content strengthen the subdomain primarily and the main domain secondarily.

Analytics simplicity: tracking visitor behavior across domain boundaries (which subdomains create) requires additional analytics configuration. Subdirectories don't have this complication.

When subdomains are genuinely appropriate

Functionally distinct services. If you're running a blog (content) and a help desk (support tickets) and a status page (uptime reporting), these are different services that might reasonably live on separate subdomains: blog.example.com, help.example.com, status.example.com.

Technical separation. If the subdomain runs on different infrastructure (a different application, a different hosting provider), the subdomain structure reflects the technical reality.

Localization. If you have country-specific subdomains (us.example.com, uk.example.com, de.example.com), the subdomain structure works because each region's content is meaningfully distinct.

Brand separation. If a subsection has its own brand identity that you don't want associated with the main brand, subdomain provides separation.

The WordPress-specific considerations

Hosting a WordPress blog at example.com/blog when the main site is on a different platform (a custom-built marketing site) requires either: hosting WordPress in a /blog subdirectory of the same server, or using a reverse proxy to make a separate WordPress installation appear at /blog.

Both setups are achievable. The reverse proxy is more work to set up but allows the two systems to be hosted separately. The subdirectory installation is simpler but requires that WordPress and the main site share the same hosting.

For sites that adopted blog.example.com because of technical complications with the subdirectory approach, the inheritance of reputation is weaker. The technical convenience came with a cost.

The migration question

Sites currently on subdomain often consider migrating to subdirectory for SEO benefit. The migration is technically possible but involves: setting up redirects from every subdomain URL to its subdirectory equivalent, updating internal links throughout both sites, re-submitting sitemaps, monitoring for 4-8 weeks as Google re-indexes.

The cost is significant. The benefit (improved reputation transfer) is real but moderate. For sites with significant existing subdomain content and strong existing rankings, the migration cost might exceed the benefit. For sites just starting out where subdomain SEO is weak, the migration is more clearly worthwhile.

The decision deserves analysis: how much traffic does the subdomain currently get? How much improvement might subdirectory provide? What's the technical migration cost? The answer varies by site.

The internal linking pattern

Whether the secondary content is on subdomain or subdirectory, internal linking from main content to secondary content (and vice versa) matters for both reputation transfer and user navigation.

The pattern that strengthens both: main domain pages link contextually to relevant secondary content. Secondary content links back to relevant main pages. The cross-linking signals topical connection and helps users discover related content.

The mistake to avoid: treating the subdomain as a separate site that doesn't link back to the main domain. The internal linking opportunity gets wasted, and the subdomain develops in isolation rather than as part of the broader site.

The blog at subdirectory specifically

For most WordPress sites adding a blog, example.com/blog is the right choice. The blog content benefits from the main domain's existing reputation. The main domain benefits from the increased content and topical breadth.

The technical setup: install WordPress at the /blog subdirectory of the main domain. Configure WordPress's site URL to include /blog. The main site (which might be a different application) handles the homepage and other primary pages; WordPress handles /blog and its sub-paths.

The setup is more involved than a fresh WordPress install at the domain root, but it's well-documented and produces the better SEO outcome.

The honest summary

For new sites adding a blog or content section, the default should be subdirectory. The exceptions (functionally distinct services, technical separation requirements, brand separation needs) are real but not the typical case.

For existing sites on subdomain considering migration, evaluate the cost-benefit specifically. The migration is real work for a moderate gain; the right decision depends on site-specific factors.

The marketing claim that subdomain has "SEO benefits" is mostly outdated. The current understanding favors subdirectory in the absence of specific reasons to use subdomain.

WordPress And Subdomain vs Subdirectory: The SEO Decision