Understanding ssl certificate requirements is no longer optional for website owners — it's essential. Whether you're running a personal blog, a business site, or an e-commerce store, SSL certificates are a fundamental part of web security, user trust, and search engine visibility. Google now flags non-HTTPS sites as "Not Secure," browsers actively warn visitors away, and many web services simply won't work without SSL.
This guide covers everything you need to know about SSL certificate requirements, from the technical basics to choosing the right type for your website.
What Is an SSL Certificate?
SSL (Secure Sockets Layer) — and its modern successor TLS (Transport Layer Security) — encrypts the connection between a visitor's browser and your web server. This encryption prevents anyone from intercepting data in transit, including passwords, credit card numbers, and personal information.
When your site has a valid SSL certificate:
- The URL shows
https://instead ofhttp:// - A padlock icon appears in the browser address bar
- Data between visitor and server is encrypted
- Search engines give you a ranking boost
Core SSL Certificate Requirements for Every Website
1. Valid Certificate from a Trusted Authority
Your SSL certificate must be issued by a trusted Certificate Authority (CA). Browsers maintain a list of trusted CAs, and certificates from unrecognised sources will trigger security warnings.
Trusted Certificate Authorities include:
- Let's Encrypt (free, automated)
- DigiCert
- Sectigo (formerly Comodo)
- GlobalSign
- GoDaddy
Self-signed certificates work for development but will scare away visitors in production — browsers display full-page warnings for untrusted certificates.
2. Certificate Must Match Your Domain
The certificate's Common Name (CN) or Subject Alternative Name (SAN) must match the domain visitors use to access your site. A certificate for example.com won't work for www.example.com unless it covers both.
Common configurations:
Single domain: example.com
With www: example.com + www.example.com
Wildcard: *.example.com (covers all subdomains)
Multi-domain: example.com + app.example.com + api.example.com
3. Certificate Must Not Be Expired
SSL certificates have a maximum validity period. As of 2026, most certificates are valid for 90 days (Let's Encrypt) to 1 year (paid certificates). An expired certificate is worse than no certificate — it displays aggressive browser warnings that immediately drive visitors away.
Set up auto-renewal to avoid expiration:
# Let's Encrypt auto-renewal (runs twice daily)
sudo certbot renew --dry-run
# Check when your certificate expires
sudo certbot certificates
# Or check manually
openssl x509 -enddate -noout -in /etc/letsencrypt/live/yourdomain.com/cert.pem
4. Complete Certificate Chain
Your server must present the complete certificate chain — your certificate plus any intermediate certificates that link it back to the root CA. A missing intermediate certificate causes errors in some browsers while working fine in others.
# Test your certificate chain
openssl s_client -connect yourdomain.com:443 -servername yourdomain.com
# Or use SSL Labs (recommended)
# https://www.ssllabs.com/ssltest/
Types of SSL Certificates: Choosing the Right One
Domain Validation (DV)
What it verifies: You control the domain
Cost: Free (Let's Encrypt) to $50/year
Best for: Blogs, personal sites, small business websites
Issuance time: Minutes
DV certificates are the most common and meet the ssl certificate requirements for the vast majority of websites. Let's Encrypt provides them for free with automated renewal.
Organisation Validation (OV)
What it verifies: Domain ownership + business identity
Cost: $50-200/year
Best for: Business websites, corporate sites
Issuance time: 1-3 days
OV certificates display your organisation's name in the certificate details, adding an extra layer of trust.
Extended Validation (EV)
What it verifies: Domain + business + legal existence
Cost: $100-500/year
Best for: E-commerce, banking, high-trust applications
Issuance time: 1-2 weeks
EV certificates require the most rigorous verification process. While browsers no longer show the green address bar, the certificate details display full company information.
Wildcard Certificates
What they cover: A domain and all its subdomains (*.example.com)
Cost: $50-300/year (or free via Let's Encrypt)
Best for: Sites with multiple subdomains
# Get a free wildcard certificate from Let's Encrypt
sudo certbot certonly --manual --preferred-challenges dns \
-d "*.yourdomain.com" -d "yourdomain.com"
Setting Up SSL: Step by Step
Option 1: Free SSL with Let's Encrypt
The easiest way to meet ssl certificate requirements for most websites:
# Install Certbot
sudo apt update
sudo apt install certbot python3-certbot-nginx -y
# Get and install certificate (Nginx)
sudo certbot --nginx -d yourdomain.com -d www.yourdomain.com
# For Apache
sudo certbot --apache -d yourdomain.com -d www.yourdomain.com
Certbot automatically configures your web server and sets up renewal.
Option 2: Cloudflare SSL (Free)
If you use Cloudflare, you get free SSL without installing anything on your server:
- Sign up for Cloudflare (free plan)
- Point your domain's nameservers to Cloudflare
- Enable "Full (Strict)" SSL mode
- Cloudflare handles certificates automatically
Option 3: Paid Certificate Installation
For OV/EV certificates:
- Generate a CSR (Certificate Signing Request) on your server
- Submit the CSR to your chosen CA
- Complete the validation process
- Download and install the certificate
# Generate a CSR
openssl req -new -newkey rsa:2048 -nodes \
-keyout yourdomain.key -out yourdomain.csr
# After receiving your certificate, configure Nginx
server {
listen 443 ssl;
server_name yourdomain.com;
ssl_certificate /path/to/yourdomain.crt;
ssl_certificate_key /path/to/yourdomain.key;
ssl_trusted_certificate /path/to/chain.crt;
}
SSL Best Practices Beyond Basic Requirements
Force HTTPS Everywhere
Redirect all HTTP traffic to HTTPS:
server {
listen 80;
server_name yourdomain.com www.yourdomain.com;
return 301 https://$host$request_uri;
}
Enable HSTS
HTTP Strict Transport Security tells browsers to always use HTTPS:
add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
Use Strong TLS Configuration
Disable outdated protocols and weak ciphers:
ssl_protocols TLSv1.2 TLSv1.3;
ssl_prefer_server_ciphers on;
ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256;
Monitor Certificate Expiration
Set up alerts so you never get caught with an expired certificate:
# Simple cron job to check expiration
0 9 * * 1 echo | openssl s_client -connect yourdomain.com:443 2>/dev/null | \
openssl x509 -noout -dates | mail -s "SSL Check" admin@yourdomain.com
Common SSL Issues and Fixes
Mixed content warnings: Your page loads over HTTPS but includes resources (images, scripts) over HTTP. Fix by updating all resource URLs to HTTPS or using protocol-relative URLs.
Certificate mismatch: The domain in the certificate doesn't match your URL. Ensure your certificate covers both yourdomain.com and www.yourdomain.com.
Intermediate certificate missing: Some browsers show warnings while others don't. Use SSL Labs to test and identify missing chain certificates.
Expired certificate: Set up auto-renewal with Certbot and monitor with external tools like UptimeRobot.
Test Your SSL Configuration
After setup, verify everything works:
# Quick command-line test
curl -vI https://yourdomain.com 2>&1 | grep -E "SSL|certificate|expire"
# Comprehensive test (recommended)
# Visit: https://www.ssllabs.com/ssltest/
# Aim for an A or A+ rating
Meet Every SSL Certificate Requirement with DeployBase
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