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Subdomain vs Subdirectory

최종 업데이트:

Definition

A subdomain adds a label before the domain: blog.example.com, shop.example.com become subdomains of example.com.

A subdirectory uses paths within the same domain: example.com/blog/, example.com/shop/ are folders separated by slashes (/).

Both divide site sections, but Google handles them differently and SEO outcomes can differ.

Summary

Conclusion: Subdirectories are advantageous in most cases. Because Google treats subdomains as separate sites, main domain authority does not transfer to subdomains. However, subdomains are reasonable when an independent technical environment is needed or operating as a completely separate service.

How Google Handles Them

Subdomain: Treated as a Separate Site

Google officially treats subdomains as separate sites. Authority and backlinks accumulated on blog.example.com do not transfer directly to example.com.

John Mueller (Google spokesperson) stated in 2018 that "treating subdomains as separate sites is common." Google may partially pass related signals when it understands the relationship, but this is not guaranteed.

Subdirectory: Treated as the Same Site

example.com/blog/ is the same site as example.com. Subdirectory backlinks and authority contribute directly to the main domain. Internal link authority flows naturally.

Subdomain vs Subdirectory Comparison

[COMPARISON_TABLE: Subdomain vs subdirectory — authority, crawl, maintenance]

Subdomain

Authority: Separated from main domain. Must build authority independently from scratch
Crawl: Googlebot allocates separate crawl budget. No impact on main site crawl
Internal links: Links between example.com and blog.example.com are technically external links
Google Search Console: Requires separate property registration (can unify with domain property)
When to use: Independent services, different tech stacks, separate team operations

Subdirectory

Authority: Shares main domain authority. Existing domain trust applies immediately
Crawl: Shares main site crawl budget. Whole-site crawl efficiency management needed
Internal links: Full internal links. Link authority transfers freely
Google Search Console: Managed under same property
When to use: Blog, wiki, news sections, support documentation

Real Example: console.alleo.pro vs alleo.wiki

The ALLEO wiki including this document is a case where an actual domain decision was made.

Subdomain approach: console.alleo.pro

  • Clear relationship as a sub-service of alleo.pro
  • Good for separating login/app-centric areas like console from marketing sites
  • Suitable for product functionality rather than search content assets

Independent domain approach: alleo.wiki

  • Completely separate brand domain
  • .wiki TLD clearly expresses content purpose
  • Starts trust from zero initially but builds independent brand value long term

Final decision: alleo.wiki (independent domain)
Reason: Console naturally fits as a service sub-area like console.alleo.pro, but Wiki is a content asset that builds its own search traffic and topic authority, making an independent domain reasonable.

When to Choose Subdomain

1. Completely Different Tech Stack

When the main site is Next.js and the blog is WordPress, subdomains are practical for technical separation.

2. Independent Team or Business Operation

HR, Support, or developer portals operated by separate teams with completely different purposes from the main site.

3. Country Sites (Instead of ccTLD)

Country subdomains like kr.example.com, jp.example.com. hreflang tags are required in this case. See hreflang Tag for details.

4. App/API

Technical endpoints users do not visit directly, such as app.example.com, api.example.com, rather than marketing sites.

When to Choose Subdirectory

1. Blog and News Sections

example.com/blog/ is the main site’s content marketing engine. Using subdirectories means blog post backlinks contribute directly to the main domain.

2. Wiki and Knowledge Base

example.com/wiki/ indexes quickly with main site authority.

3. Product Documentation

example.com/docs/ shares product site authority for faster search visibility.

4. Multilingual Services

Language subdirectories like example.com/ko/, example.com/en/ plus hreflang is the simplest way to operate multilingual sites without ccTLDs.

Migration: Subdomain to Subdirectory

When moving existing blog.example.com to example.com/blog/:

  1. Copy content to new subdirectory
  2. Set 301 redirects from each subdomain URL to corresponding subdirectory URL
  3. Update XML sitemap
  4. Register new URLs in GSC + request crawl
  5. Request external backlink updates (301 passes link authority, but updates take time)

Over 3–6 months after migration, subdirectory content may absorb main domain authority and rankings may improve.

Korea Market Application

Naver Handling

Naver handles subdomains and subdirectories similarly to Google but operates its own services (Blog, Cafe) as subdomains. blog.naver.com/username is Naver platform’s subdomain structure. External site operators are recommended to use subdirectories on their own domains, same as Google.

See Naver SEO for details.

Common Mistake Among Korean Companies

Large Korean corporations tend to overuse subdomains like product.company.com, support.company.com per product/service. Each subdomain must build authority independently, dispersing SEO efficiency. Consolidating under one strong domain with subdirectories is better for authority concentration.

Frequently Asked Questions

Q. Does Google really treat subdomains as separate sites?
A. Officially yes. Google Search Central documentation and multiple official statements from John Mueller state subdomains are handled as separate sites. Google may pass some trust when it understands the relationship, so "generally separate" is more accurate than "completely separate."

Q. Should I migrate a blog already running on a subdomain?
A. If the subdomain blog has many accumulated backlinks, migration carries short-term risk. Migrate when consolidation benefits (main domain authority integration) outweigh costs (recrawl recognition period, temporary ranking drop). Small blogs have clear migration benefits. Large blogs should decide after consulting experts.

Q. Is www a subdomain?
A. Technically www.example.com is a subdomain. However, Google treats www.example.com and example.com as essentially the same site; unifying with 301 redirect is recommended. See Duplicate Content for details.

Q. Do subdomains for CDN or image serving affect SEO?
A. Technical subdomains users do not visit directly, such as cdn.example.com or images.example.com, do not directly affect SEO. Limiting crawl with robots.txt on such subdomains is recommended.

Q. What about SaaS companies using customer subdomains (customer.saas.com)?
A. Customer subdomains are a business requirement choice, separate from SEO optimality. When needed, set appropriate meta tags and canonicals so each customer subdomain can appear in search results independently, and noindex sensitive customer data pages.

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