How to Create and Configure Subdomains: A Step-by-Step Guide
Creating a subdomain involves two main steps: adding a DNS record for the subdomain, and configuring your web server to handle requests to it. The exact process varies by hosting provider and server software, but the underlying concepts are universal.
Step 1: Add a DNS Record
Log in to wherever you manage your domain's DNS — your domain registrar (Namecheap, GoDaddy, Google Domains), your hosting control panel (cPanel, Plesk), or your DNS provider (Cloudflare, Route 53). Navigate to the DNS management area for your domain and add a new record.
For most use cases, create an A record with the subdomain prefix as the Name/Host field and the server's IP address as the Value. Example: Name = "blog", Value = "192.0.2.1", TTL = 3600. If you want the subdomain to point to another hostname (like a hosting service's domain), use a CNAME record instead: Name = "blog", Value = "your-server.hosting-provider.com".
Step 2: Configure Your Web Server
Nginx server block: Add a new server block in your Nginx configuration: server {{ listen 80; server_name blog.example.com; root /var/www/blog; index index.html; }}. Reload Nginx after changes: sudo nginx -s reload.
Apache virtual host: Add a VirtualHost block: <VirtualHost *:80> ServerName blog.example.com DocumentRoot /var/www/blog </VirtualHost>. Enable with a2ensite and reload Apache.
cPanel hosting: Many shared hosting providers offer a "Subdomains" section in cPanel where you can create a subdomain by entering the prefix, selecting the parent domain, and specifying a document root directory. cPanel handles both DNS and server configuration automatically.
Step 3: Enable HTTPS
Each subdomain requires its own SSL certificate (or a wildcard certificate covers them all). With Let's Encrypt/Certbot: sudo certbot --nginx -d blog.example.com obtains and installs a free certificate. A wildcard certificate (*.example.com) covers all subdomains but requires DNS validation during issuance. For high-volume subdomain creation (multi-tenant apps), wildcard certificates are essentially mandatory.
Verifying Your Setup
Test DNS resolution: dig blog.example.com or nslookup blog.example.com should return the expected IP address. Test HTTP connectivity: curl -I http://blog.example.com should return a 200 or appropriate redirect. Check SSL: curl -I https://blog.example.com should show a valid certificate in the response headers.
Learn about subdomain SEO considerations or explore our DNS lookup tools to check subdomain configurations.