domaindetails.com
Knowledge Base/Getting Started/What is a Subdomain and When Should You Use One? (2025 Guide)
Getting Started

What is a Subdomain and When Should You Use One? (2025 Guide)

Learn what subdomains are, how they work, and when to use them. Discover common subdomain examples, SEO implications, and best practices for organizing your website.

8 min
Published 2025-03-22
Updated 2025-11-15
By DomainDetails Team

Quick Answer

A subdomain is a prefix added before your main domain name, like blog.example.com or shop.example.com. It creates a separate section of your website with its own content, design, and functionality while remaining part of your main domain. Subdomains are free to create, help organize large websites, and are commonly used for blogs, stores, mobile sites, and regional content.

Table of Contents

Understanding Subdomains

A subdomain is an additional part of your main domain name that appears before it.

Anatomy of a Subdomain:

https://blog.example.com
       │    │       │
       │    │       └── [Top-Level Domain](/kb/getting-started/understanding-domain-extensions) (.com)
       │    └──────────── Root/Apex Domain (example)
       └───────────────── Subdomain (blog)

Key Characteristics:

What it is:

  • A prefix to your domain
  • Part of your domain hierarchy
  • A separate "section" of your website

What it does:

  • Creates distinct website sections
  • Organizes content logically
  • Allows different hosting/configurations

What it costs:

  • Usually free (included with domain registration)
  • No additional registration fees
  • Same as your main domain costs

Think of It Like This:

Your domain is a house:

  • example.com = The main house

Subdomains are separate rooms:

  • blog.example.com = The library
  • shop.example.com = The retail space
  • support.example.com = The help desk

Each room (subdomain) can have different:

  • Furniture (design)
  • Purpose (function)
  • Rules (settings)

But they're all still part of the same house (domain).

How Subdomains Work

DNS Perspective:

From a technical standpoint, subdomains are completely separate entities:

example.com → Points to IP 192.0.2.1 (main site)
blog.example.com → Points to IP 192.0.2.2 (different server)
shop.example.com → Points to IP 198.51.100.1 (another server)

Each subdomain can:

  • Point to a different server/hosting
  • Have different DNS records
  • Use different technologies
  • Be hosted by different companies

Browser Perspective:

When you visit a subdomain:

Step 1: Browser requests blog.example.com Step 2: DNS looks up blog.example.com specifically Step 3: Returns the IP address for that subdomain Step 4: Browser connects to that server Step 5: Loads the subdomain's content

The browser treats blog.example.com as completely different from example.com or shop.example.com.

Cookies and Sessions:

Important technical detail:

  • Cookies from example.com don't automatically work on blog.example.com
  • User sessions don't carry over by default
  • Each subdomain is a separate "origin" in security terms

This affects login systems, shopping carts, and tracking.

Subdomain vs Domain vs Path

Understanding the difference is crucial for making the right choice:

Subdomain:

blog.example.com

Structure: prefix.domain.extension Example: blog.example.com, shop.example.com Separate: Technically distinct from main domain SEO: Treated as separate site by Google

Root/Apex Domain:

example.com

Structure: domain.extension Example: google.com, amazon.com Main site: The primary domain SEO: Your main domain authority

Path/Subfolder:

example.com/blog

Structure: domain.extension/path Example: example.com/shop, example.com/about Part of: Main domain SEO: Contributes to main domain authority

Side-by-Side Comparison:

Feature Subdomain Subfolder
Example blog.example.com example.com/blog
Technical setup Separate DNS record Same domain, just a path
Hosting Can be different server Usually same server
SEO treatment Separate site Part of main site
Domain authority Separate Contributes to main
Setup difficulty Medium Easy
Best for Different platforms/purposes Content organization

www is a Subdomain:

Technically, www.example.com is a subdomain!

www.example.com
│
└── Subdomain prefix

It's so common that most people don't think of it that way. Many sites redirect:

Both point to the same content.

Common Subdomain Examples

Real companies use subdomains extensively. Here are popular patterns:

1. Blog Subdomains

Format: blog.example.com

Real examples:

  • blog.hubspot.com - HubSpot's marketing blog
  • blog.google.com - Google's official blog
  • blog.mailchimp.com - Mailchimp's marketing resources

Why:

  • Separates content from product
  • Can use different CMS (WordPress vs main site)
  • Easier to manage large content libraries

2. E-commerce/Shop Subdomains

Format: shop.example.com, store.example.com

Real examples:

  • shop.tesla.com - Tesla merchandise
  • store.steampowered.com - Steam game store
  • shop.lululemon.com - Lululemon online store

Why:

  • E-commerce platforms (Shopify) easier on subdomain
  • Separate checkout/cart functionality
  • Different security requirements

3. Support/Help Subdomains

Format: support.example.com, help.example.com

Real examples:

  • support.google.com - Google support center
  • help.netflix.com - Netflix help pages
  • support.apple.com - Apple support

Why:

  • Dedicated support platform
  • Different search/organization needs
  • Can use specialized help desk software

4. Mobile Subdomains

Format: m.example.com, mobile.example.com

Real examples:

  • m.facebook.com - Facebook mobile (though less common now)
  • m.youtube.com - YouTube mobile site

Why:

  • (Historically) Separate mobile version
  • Note: Less common in 2025 due to responsive design

5. Regional/Language Subdomains

Format: uk.example.com, de.example.com

Real examples:

  • uk.linkedin.com - LinkedIn UK
  • de.wikipedia.org - German Wikipedia
  • ca.indeed.com - Indeed Canada

Why:

  • Localized content
  • Regional pricing/products
  • Language-specific content

6. App/Platform Subdomains

Format: app.example.com, platform.example.com

Real examples:

  • app.slack.com - Slack application
  • studio.youtube.com - YouTube Studio
  • app.asana.com - Asana web app

Why:

  • Separates marketing site from application
  • Different tech stack for web app
  • Clearer user experience

7. Testing/Staging Subdomains

Format: staging.example.com, dev.example.com, beta.example.com

Why:

  • Test new features before launch
  • Development environment
  • QA and debugging
  • Usually not public-facing

8. API Subdomains

Format: api.example.com, developers.example.com

Real examples:

  • api.github.com - GitHub API
  • api.twitter.com - Twitter API
  • developer.amazon.com - Amazon Web Services

Why:

  • Separates API from main site
  • Different rate limiting/caching
  • Developer-focused content

When to Use Subdomains

Subdomains make sense in specific scenarios:

✅ Good Reasons to Use Subdomains:

1. Different Platform/Technology

Main site: example.com (Custom CMS)
Blog: blog.example.com (WordPress)
Shop: shop.example.com (Shopify)
App: app.example.com (React SPA)

Why: Each platform runs independently without conflicts.

2. Separate Hosting

Main site: example.com (Hostgator)
Blog: blog.example.com (WP Engine)

Why: You can use specialized hosting for each need.

3. Large Content Sections

support.example.com - 10,000+ help articles
docs.example.com - Technical documentation
community.example.com - User forum

Why: Easier to manage and scale separately.

4. Regional/Language Sites

example.com - English (global)
de.example.com - German site
jp.example.com - Japanese site

Why: Different content, pricing, regulations per region.

5. Testing and Development

staging.example.com - Test new features
dev.example.com - Development environment
beta.example.com - Beta users testing

Why: Isolate testing from production.

6. Mobile-Specific Version

m.example.com - Mobile-optimized site

Why: (Historically used, though responsive design is now standard)

7. Separating Web App from Marketing

example.com - Marketing and info
app.example.com - Actual application

Why: Different user journey and purpose.

8. User-Generated Subdomains

john.example.com - John's profile
company.example.com - Company page

Why: Give users custom URLs (like Tumblr, Medium).

When NOT to Use Subdomains

Subdomains aren't always the answer:

❌ Don't Use Subdomains When:

1. Simple Content Organization

Wrong:

about.example.com
services.example.com
contact.example.com

Right:

example.com/about
example.com/services
example.com/contact

Why: Subfolders are simpler and better for SEO.

2. Building Domain Authority

Problem: Subdomains split SEO authority

blog.example.com - Separate domain authority
example.com - Separate domain authority

Better: example.com/blog builds main domain authority

3. Small Websites

If your entire site is <50 pages, you don't need subdomains. Keep it simple with one domain.

4. When You Want Unified Analytics

Subdomains complicate:

  • Google Analytics tracking
  • Conversion funnels
  • User journey mapping

5. E-commerce on Small Scale

Modern approach:

example.com/shop

Why: Most modern platforms (WooCommerce, Shopify integrations) work fine on main domain.

6. For "Organization" That Doesn't Matter

Don't create subdomains just because you can:

news.example.com (3 blog posts)
products.example.com (1 product)

Overkill! Use subfolders instead.

Subdomains and SEO

The SEO implications of subdomains are important to understand:

How Google Treats Subdomains:

Official Google stance:

"Google Web Search is fine with using either subdomains or subdirectories."

Reality: There are differences.

Subdomains = Separate Sites

Google can treat subdomains as separate websites:

example.com - Domain Authority: 45
blog.example.com - Domain Authority: 20

Implications:

  • Backlinks to blog.example.com don't fully benefit example.com
  • Domain authority is split
  • Rankings must be built separately
  • Separate indexing and crawling

Subfolders = One Site

example.com/blog - Contributes to main domain

Implications:

  • All backlinks benefit main domain
  • Consolidated domain authority
  • Easier to rank
  • Unified SEO strategy

When Subdomains Help SEO:

1. Keyword Targeting

seattle.example.com - Ranks for "Seattle [service]"
blog.example.com - Keyword-rich content doesn't dilute main site

2. International SEO

uk.example.com - Signals UK content
de.example.com - Signals German content

Google can geotarget these appropriately.

3. Topic Authority

health.example.com - All health content
finance.example.com - All finance content

Can build niche topical authority.

When Subdomains Hurt SEO:

1. Splitting Authority Your domain authority gets divided instead of consolidated.

2. Internal Linking Complexity Links between subdomains count as external links (less valuable).

3. Duplicate Content Risk Same content on blog.example.com and example.com/blog = problem.

4. Crawl Budget Google might not crawl all your subdomains thoroughly.

SEO Best Practices:

If using subdomains:

  1. ✅ Create unique, valuable content on each
  2. ✅ Set up separate Google Search Console properties
  3. ✅ Build backlinks to each subdomain independently
  4. ✅ Use consistent branding across subdomains
  5. ✅ Cross-link between subdomains and main domain
  6. ✅ Submit separate sitemaps for each

Default recommendation: Unless you have a specific technical reason, use subfolders (example.com/blog) for better SEO.

How to Create a Subdomain

Creating a subdomain is straightforward:

Step 1: Access Your DNS Settings

Where: Your domain registrar or DNS host (Cloudflare, Route 53, etc.)

Login to:

  • Namecheap Advanced DNS
  • GoDaddy DNS Management
  • Cloudflare DNS
  • cPanel (if hosting provides it)

Step 2: Add DNS Record

Create an A record or CNAME record:

A Record (points to IP):

Type: A
Name: blog
Value: 192.0.2.1 (your server IP)
TTL: 3600 (1 hour)

CNAME Record (points to another domain):

Type: CNAME
Name: blog
Value: example.com
TTL: 3600

Step 3: Wait for Propagation

DNS changes take 24-48 hours to fully propagate, though often work within minutes.

Check propagation:

  • Visit blog.example.com
  • Use whatsmydns.net
  • Use dnschecker.org

Step 4: Configure Hosting

If same server as main domain:

  • Add subdomain in cPanel/hosting panel
  • Point to specific folder
  • Configure SSL certificate

If different server:

  • Ensure DNS points to correct IP
  • Set up virtual host/server block
  • Install SSL certificate for subdomain

Step 5: Add Content

  • Upload website files
  • Install CMS if needed
  • Configure and test

Common Hosting Panel Methods:

cPanel:

  1. Go to "Subdomains" section
  2. Enter subdomain name (blog)
  3. Select document root folder
  4. Click "Create"

Plesk:

  1. Go to "Subdomains"
  2. Click "Add Subdomain"
  3. Enter name and path
  4. Save

Cloudflare:

  1. DNS section
  2. Add record
  3. Type: A or CNAME
  4. Name: your subdomain
  5. Content: IP or target
  6. Save

Subdomain Best Practices

Naming Conventions:

Do:

  • ✅ Use descriptive names (blog, shop, support)
  • ✅ Keep it short and memorable
  • ✅ Match the subdomain's purpose
  • ✅ Be consistent with naming patterns

Don't:

  • ❌ Use numbers or hyphens
  • ❌ Make it too long (blogandnewsandarticles.example.com)
  • ❌ Use confusing abbreviations
  • ❌ Choose names similar to competitors

SSL Certificates:

Each subdomain needs SSL:

Option 1: Wildcard SSL

*.example.com - Covers all subdomains

Cost: $50-200/year Pros: Covers unlimited subdomains Cons: More expensive

Option 2: Individual SSL

example.com
blog.example.com
shop.example.com

Cost: Free (Let's Encrypt) to $50/each Pros: More control Cons: Manage multiple certificates

Recommendation: Let's Encrypt offers free SSL for all subdomains.

Branding Consistency:

Maintain unified branding:

  • Same logo across all subdomains
  • Consistent header/footer
  • Similar design language
  • Clear navigation between subdomains

Example - Good:

example.com - Main brand
blog.example.com - Same header/logo
shop.example.com - Consistent colors/fonts

Security:

Each subdomain is a potential entry point:

  • Keep all platforms updated
  • Use strong passwords per subdomain
  • Monitor for vulnerabilities
  • Implement HTTPS everywhere
  • Consider Web Application Firewall (WAF)

Performance:

Optimize each subdomain:

  • Use CDN for static content
  • Implement caching
  • Optimize images
  • Minimize redirects between subdomains

Frequently Asked Questions

Do subdomains cost money?

No! Subdomains are free to create once you own the main domain. You can create unlimited subdomains at no additional cost.

However, you may need to pay for:

  • Hosting (if using separate hosting)
  • SSL certificates (or use free Let's Encrypt)
  • Premium features on your hosting plan

Can I create unlimited subdomains?

Technically yes, but:

  • Some hosting plans limit subdomain count
  • Managing too many becomes complex
  • Each one needs maintenance and security updates
  • DNS has practical limits (though very high)

Practical limit: Most people use 5-15 subdomains max.

Are subdomains good or bad for SEO?

It depends:

Good when:

  • You have genuinely different sections
  • Each subdomain has substantial unique content
  • You need different technical platforms

Bad when:

  • Used just for organization (use subfolders instead)
  • Splits your domain authority unnecessarily
  • Creates duplicate content

Google's stance: They can handle both, but subfolders often work better for SEO.

Can I redirect a subdomain to my main domain?

Yes! Very common:

blog.example.com → example.com/blog (301 redirect)

Why do this:

  • Consolidating SEO authority
  • Restructuring your site
  • Retiring old subdomains

How: Configure redirect in:

  • .htaccess file
  • Server configuration
  • Cloudflare page rules
  • Hosting control panel

What's the difference between subdomain and addon domain?

Subdomain:

blog.example.com (part of example.com)

Addon domain:

newbusiness.com (completely separate domain)

Key difference: Subdomains are part of your main domain; addon domains are separate domains hosted on same account.

Can I have www and a subdomain?

Yes! These are all valid:

www.example.com
blog.example.com
shop.example.com
www.blog.example.com (though uncommon)

Most people use either www OR no prefix, but technically you can combine them.

How many levels deep can subdomains go?

Technically, very deep:

sub3.sub2.sub1.example.com

Practical limit: 1-2 levels max. More than that is confusing and rarely necessary.

Do I need separate hosting for a subdomain?

No! Subdomains can:

  • Share hosting with main domain (most common)
  • Use different hosting (if needed)
  • Point anywhere you want

Same hosting example:

example.com → /public_html/
blog.example.com → /public_html/blog/

Key Takeaways

✓ Subdomains are prefixes to your domain - blog.example.com, shop.example.com

✓ Free to create - no additional registration fees beyond your main domain cost

✓ Treated as separate sites by Google - SEO authority doesn't fully transfer between them

✓ Best for different platforms or hosting - WordPress blog while main site uses different CMS

✓ Common uses include - blogs, stores, support centers, mobile sites, regional content

✓ Consider subfolders first - example.com/blog often better for SEO than blog.example.com

✓ Each subdomain needs its own SSL certificate - use free Let's Encrypt or wildcard SSL

✓ Setup is simple - just add a DNS record and configure hosting

✓ Used by major sites - blog.hubspot.com, support.google.com, app.slack.com

✓ Not a substitute for poor organization - don't use subdomains just to "organize" small sites

Next Steps

Now that you understand subdomains, here's what to do:

Ready to Create One?

  1. Learn the process: How to Add a Subdomain to Your Website (Coming Soon)
  2. Understand DNS: How to Update Domain Nameserver Records
  3. Compare options: Addon Domain vs Parked Domain vs Subdomain (Coming Soon)

Learn More Fundamentals:

  1. Domain basics: What is a Domain Name? Complete Beginner's Guide
  2. Domain structure: Understanding Second-Level Domains (SLDs)
  3. DNS system: What is DNS? Domain Name System Explained

Advanced Topics:

  1. SEO considerations: Domain Name SEO Benefits Explained
  2. Technical setup: Setting Up DNSSEC for Your Domain (Coming Soon)
  3. Security: Domain Security Best Practices for Businesses

Research Sources

This article was researched using current 2025 information:

Beginners to intermediate

Related Articles

What is a Domain Name? Complete Beginner's Guide (2025)

Learn what a domain name is, how it works, and why you need one. Simple explanations, real-world examples, and everything beginners need to know about domain names.

Getting Started
8 min

Understanding Second-Level Domains (SLDs): Complete Guide

Learn what second-level domains are, how they differ from TLDs and subdomains, and why they're the most important part of your domain name. Complete guide with examples.

Getting Started
9 min