How to Set Up a Wildcard DNS Record

What Is a Wildcard Record?

A wildcard DNS record matches all subdomains that do not have an explicit record. It uses an asterisk (*) as the subdomain name.

*.example.com.    300    IN    A    198.48.63.241

This means anything.example.com resolves to your server, unless a specific record exists for that subdomain.

Use Cases

• Multi-tenant SaaS applications (tenant1.example.com, tenant2.example.com)
• User-generated subdomains (username.example.com)
• Development environments (feature-123.dev.example.com)
• Catch-all for mistyped subdomains

Setting Up

At your DNS provider, create an A record with the name *:

Nginx Catch-All Server Block

server {
    listen 80;
    server_name *.example.com;

    # Extract subdomain
    set $subdomain "";
    if ($host ~* "^(.+)\.example\.com$") {
        set $subdomain $1;
    }

    root /var/www/sites/$subdomain/public;
    # Or proxy to an application that handles routing
}

Wildcard SSL with Let's Encrypt

# Requires DNS challenge (not HTTP)
sudo certbot certonly --manual --preferred-challenges dns -d "*.example.com" -d "example.com"

You will be prompted to create a DNS TXT record at _acme-challenge.example.com.

Important Notes

• Wildcard records only match one level: *.example.com matches foo.example.com but NOT foo.bar.example.com
• Explicit records take priority over wildcards
• MX records should NOT use wildcards