How to Secure Your Entire Domain with Let’s Encrypt Wildcard Certificates in 2025

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In an era where digital trust and data security are more vital than ever, establishing and maintaining a secure connection across your entire online presence has become critical. Fortunately, securing your domain doesn’t have to be expensive or overly complex. With Let’s Encrypt, an organization that provides free SSL/TLS certificates, and the growing adoption of wildcard certificates, even large, dynamic websites can implement HTTPS across all of their subdomains with minimal effort and at no cost.

This article will walk you through how to secure your entire domain using Let’s Encrypt wildcard certificates in 2025. By the end, you’ll understand what wildcard certificates are, why they matter, and how to implement them for comprehensive domain protection using the latest best practices.

What Are Let’s Encrypt Wildcard Certificates?

Let’s Encrypt wildcard certificates are SSL/TLS certificates that allow you to secure all the subdomains of a given domain using a single certificate. Unlike standard certificates which need to be issued separately for every subdomain (e.g., www.example.com, blog.example.com), a wildcard certificate for *.example.com covers all those subdomains and any others you might add later.

Key advantages of wildcard certificates:

  • Simplified management: One certificate for all subdomains reduces administrative overhead.
  • Flexible scalability: New subdomains are automatically covered.
  • Cost-effective: With Let’s Encrypt, wildcard certificates are free.

Requirements for Wildcard Certificates with Let’s Encrypt

To issue wildcard certificates using Let’s Encrypt, you’ll need to use the DNS-01 challenge method for domain validation. Other validation methods like HTTP-01 are not available for wildcard issuance due to security considerations.

Before you begin, ensure that you have:

  • Access to your domain’s DNS records
  • A Linux-based server (for CLI tools like Certbot)
  • Sudo privileges or administrative access

For most users, the Certbot client is the preferred tool to request wildcard certificates from Let’s Encrypt.

[h2]Step-by-Step Guide to Securing Your Domain

Step 1: Install Certbot

Certbot is the official client maintained by the Electronic Frontier Foundation (EFF) to issue certificates from Let’s Encrypt. Install it on your server using the method appropriate for your operating system.

sudo apt update
sudo apt install certbot

Confirm Certbot is installed:

certbot --version

Step 2: Prepare for DNS-01 Challenge

Since you need to prove ownership of the domain using DNS-01, Certbot will ask you to create a TXT record in your domain’s DNS settings. Some DNS providers support automation through APIs, which can vastly simplify this process.

Manual method: If your DNS provider doesn’t support automation, you’ll need to create a TXT record manually when prompted. Certbot will provide the record details during certificate issuance.


Step 3: Issue the Wildcard Certificate

Use the following Certbot command to initiate the request for a wildcard certificate:

sudo certbot -d "*.example.com" --manual --preferred-challenges dns certonly

Replace example.com with your actual domain. Certbot will produce TXT record details that you must enter into your DNS settings.

Step 4: Verify and Obtain the Certificate

After creating the TXT record, wait a few minutes for DNS propagation before pressing Enter in your terminal. If everything is set up correctly, Certbot will successfully issue your wildcard certificate, which will be saved to a default location like:

/etc/letsencrypt/live/example.com/

The key files you’ll use in your web server configuration are:

  • fullchain.pem: Your signed certificate and chain
  • privkey.pem: Your private key

Step 5: Configure Your Web Server

After obtaining the certificate, configure your web server (Apache, NGINX, etc.) to use the new certificate files. Let’s use NGINX as an example:

server {
    listen 443 ssl;
    server_name *.example.com;

    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

    # Additional configuration...
}

Restart NGINX to apply changes:

sudo systemctl restart nginx

Step 6: Automate Renewal

Let’s Encrypt certificates expire every 90 days. Automating renewal ensures continuous HTTPS availability without manual intervention.

To dry-run an automated renewal:

sudo certbot renew --dry-run

If the renewal is successful, you can add a cron job or systemd timer to handle automatic renewals. Certbot often sets this up by default during installation.

Step 7: Security Best Practices

Wildcard certificates are powerful but must be handled with care. Here’s how you can secure your certificates and infrastructure:

  • Restrict file permissions: Use strict file permissions for private key files.
  • Use strong HTTPS settings: Enforce TLS 1.2 or higher and disable weak ciphers.
  • Deploy HTTP Strict Transport Security (HSTS): This signals browsers to only connect via HTTPS.
  • Enable OCSP stapling: This improves certificate status checking and increases performance.

You may want to use online tools like SSL Labs’ SSL Test to evaluate your configuration for potential vulnerabilities.


Limitations of Wildcard Certificates

Despite their benefits, wildcard certificates have some important limitations:

  • They do not cover nested subdomains like sub.sub.example.com.
  • They make certificate sharing across many services easier, which means a single compromised key could expose multiple systems.
  • DNS-01 validation can be tricky if your DNS provider or setup lacks API integration for automation.

For more intricate environments, consider segmenting certificates across different services and using tools like ECDSA keys for additional security granularity.

Alternatives and Enhancements

Let’s Encrypt certificates can be complemented with other security solutions. Depending on your needs:

  • Use multi-domain (SAN) certificates if you need to secure a set of non-related domains.
  • Consider ACME-compliant DNS providers if you are aiming for full automation.
  • Implement a central certificate management tool for large-scale environments.

Conclusion

In 2025 and beyond, ensuring the security and integrity of your online services is more essential than ever. With Let’s Encrypt offering free, trusted wildcard certificates, organizations now have a simple yet robust method to secure all subdomains of a domain under HTTPS.

By following the steps outlined above, you can take advantage of modern cryptographic standards, meet compliance requirements, and provide your users with a secure and trustworthy browsing experience—all without breaking the bank.

Don’t underestimate the ripple effect of good certificate hygiene. Setting up HTTPS correctly today can help you avoid security breaches, lost trust, and major administrative headaches tomorrow.