A subdomain lives in front of your root domain (blog.example.com), while a subdirectory sits inside it as a folder path (example.com/blog). Both can host the same content, but the choice changes how search engines pass authority around your site, and that has real consequences for traffic.
The short answer is that subdirectories win for most small businesses. The longer answer, which is the one worth reading, is that the right choice depends on what you’re actually building.
The Definitions
A subdomain is technically a separate hostname. blog.example.com, shop.example.com, and help.example.com are all subdomains. Each can run on different servers, use different software, and be managed by different teams.
A subdirectory is just a folder on your existing site. example.com/blog, example.com/shop, and example.com/help are all subdirectories of the same hostname. They share the same server, SSL certificate, and general technical setup.
| Feature | Subdomain | Subdirectory |
|---|---|---|
| URL format | blog.example.com | example.com/blog |
| Hosting | Can be separate | Same as root |
| Tech stack | Can differ | Same as root |
| Link equity flow | Less consolidated | More consolidated |
| Setup complexity | Higher | Lower |
What Google Says, and What Actually Happens
Google’s public position, repeated for years by John Mueller, is that subdomains and subdirectories on the same root domain are treated as part of the same site for crawling and indexing.
In practice, that’s not the whole story. Subdomains are often evaluated with at least some independence, particularly when it comes to topical authority and how link equity distributes. When you build a blog on a subdomain, the authority you earn from inbound links tends to pool around that subdomain rather than flowing cleanly back to your main marketing site. Move that same blog to a subdirectory and the consolidation is tighter, more predictable, and historically more favourable in case studies.
The honest framing: Google can treat them the same, but it doesn’t always, and the variance almost always favours the subdirectory.
When a Subdomain Genuinely Makes Sense
- Separate applications. Your main site is a marketing brochure on WordPress, but your customer dashboard is a React app. app.example.com is appropriate.
- Different tech stacks that can’t coexist. A subdomain is a clean break.
- Multilingual sites where country TLDs aren’t an option. A French subdomain (fr.example.com) is reasonable when example.fr isn’t available.
- Different teams owning different sections. If your support docs are owned by a separate team running their own help desk software.
- Staging and development environments. staging.example.com is standard.
When a Subdirectory Is the Right Default
- Blogs and content hubs for a primary business site
- Resource centres, guides, learning sections
- Service or product category pages
- Landing pages for campaigns tied to the main brand
- Most small-business marketing sites where one team owns everything
If you’re a small business with one website, one team, and one marketing goal, your blog belongs at example.com/blog.
The Migration Question
If you already have a blog on a subdomain, migrating to subdirectory often produces noticeable traffic gains within a few months. That said, a migration is technical with real risk.
The basic checklist: map every old URL to its new location, set up 301 redirects for each, update internal links to point to the new structure, resubmit your sitemap in Search Console, and watch your logs for crawl errors. If any of that made you nervous, get help before you start.
Common Mistakes on Client Audits
- Choosing a subdomain because hosting was easier. The hosting convenience saves an afternoon. The SEO cost can run for years.
- Building a blog on a subdomain then wondering why the main site doesn’t rank. The blog has been doing the work, but the main site isn’t getting full credit.
- Using a subdomain to separate languages on a small site. Subdirectories with proper hreflang are usually simpler and more effective.
- Treating staging subdomains as live. If staging.example.com is indexable, you’ll create duplicate content issues. Block it.
- Migrating without proper redirects. Switching without 301s loses everything you were trying to consolidate.
When to Ignore the Debate Entirely
If you’re running a small local business with fifteen pages and a blog that publishes once a month, the difference is largely academic. You’ll get more value from one good piece of content than from any structural choice at this scale.
Pick the subdirectory anyway. It’s free insurance for the day your site grows.
Setting Either One Up in WordPress
Subdirectory: For most WordPress users, this is what you already have. Your blog at example.com/blog is just a category or the default posts URL. For a separate WordPress install in /blog/, use your host’s file manager or one-click installer.
Subdomain: Create the subdomain in your host’s control panel, then install WordPress into that folder. Treat it as a separate site for backups and security updates, because it is one.
The Bottom Line
Default to a subdirectory for anything that’s part of your main marketing site. Use a subdomain when you’re genuinely separating an app, a stack, a language, or a team. If you’re already on a subdomain and your blog has been doing serious work, consider a migration, but plan it properly.