SSL/TLS certificates are essential for website security, but they require regular monitoring
to ensure they're valid and properly configured. This guide will show you multiple methods
to check SSL certificates, from simple online tools to advanced command-line techniques.
Method 1: Using Our Free SSL Checker Tool (Easiest)
The fastest and easiest way to check an SSL certificate is using our free online tool:
- Visit the SSL Checker: Go to our SSL Certificate Checker
- Enter Your Domain: Type your domain name (e.g., example.com) - no need for
"https://" or "www"
- Click Check: Click the "Check SSL Certificate" button
- Review Results: View detailed information about your certificate including:
- Certificate validity status
- Expiration date and days remaining
- Issuing Certificate Authority
- Certificate chain validation
- Common name and subject alternative names
- Signature algorithm and key strength
💡 Pro Tip: Bookmark our SSL Checker and check your certificates
monthly, especially 30-60 days before expiration to avoid downtime.
Method 2: Using Your Web Browser
All modern web browsers allow you to view SSL certificate details:
Google Chrome
- Visit your website (https://yourdomain.com)
- Click the padlock icon in the address bar
- Click "Connection is secure"
- Click "Certificate is valid" to view full details
Mozilla Firefox
- Visit your website
- Click the padlock icon
- Click "Connection secure" → "More information"
- Click "View Certificate"
Safari
- Visit your website
- Click the padlock icon
- Click "Show Certificate"
Method 3: Using OpenSSL Command Line
For advanced users and system administrators, OpenSSL provides powerful command-line tools:
Check SSL Certificate from a Remote Server
openssl s_client -connect example.com:443 -servername example.com < /dev/null 2>/dev/null | openssl x509 -noout -dates
Check Certificate Expiration Date
echo | openssl s_client -servername example.com -connect example.com:443 2>/dev/null | openssl x509 -noout -enddate
View Full Certificate Details
echo | openssl s_client -servername example.com -connect example.com:443 2>/dev/null | openssl x509 -noout -text
Check Certificate Chain
openssl s_client -connect example.com:443 -showcerts
Method 4: Using cURL
cURL can also be used to check SSL certificates:
curl -vI https://example.com 2>&1 | grep -A 10 "SSL certificate"
What to Look For When Checking SSL Certificates
1. Certificate Validity
Ensure the certificate is currently valid (not expired and not yet valid):
- Valid From: The date when the certificate becomes valid
- Valid To: The expiration date
- Days Remaining: How many days until expiration
2. Certificate Issuer
Verify the certificate is issued by a trusted Certificate Authority (CA):
- Let's Encrypt
- DigiCert
- Sectigo (formerly Comodo)
- GlobalSign
- GoDaddy
3. Domain Name Match
The certificate's Common Name (CN) or Subject Alternative Names (SANs) must match your domain:
- Exact match:
example.com
- Wildcard:
*.example.com (covers all subdomains)
- Multiple domains: Listed in Subject Alternative Names
4. Certificate Chain
A complete certificate chain includes:
- End-entity certificate: Your domain's certificate
- Intermediate certificate(s): Links to the root CA
- Root certificate: Trusted by browsers (usually not sent)
5. Key Strength
Modern certificates should use:
- Minimum: 2048-bit RSA key
- Recommended: 4096-bit RSA or 256-bit ECC
- Avoid: 1024-bit or smaller (insecure)
6. Signature Algorithm
Use modern signature algorithms:
- ✅ SHA-256 with RSA (recommended)
- ✅ SHA-384 or SHA-512 (even better)
- ❌ SHA-1 (deprecated, insecure)
- ❌ MD5 (deprecated, insecure)
Common SSL Certificate Issues
🔴 Certificate Expired
Problem: The certificate has passed its expiration date.
Solution: Renew your certificate immediately. Most CAs send renewal reminders 30-90 days
before expiration.
🔴 Certificate Not Yet Valid
Problem: The system clock is wrong, or the certificate was installed before its validity
period.
Solution: Check your server's system time and date. Ensure it's synchronized with NTP.
🔴 Name Mismatch
Problem: The domain name doesn't match the certificate.
Solution: Obtain a new certificate for the correct domain, or use a
wildcard/multi-domain certificate.
🔴 Incomplete Certificate Chain
Problem: Intermediate certificates are missing.
Solution: Install the complete certificate chain provided by your CA.
🔴 Self-Signed Certificate
Problem: The certificate is not issued by a trusted CA.
Solution: Obtain a certificate from a trusted CA like Let's Encrypt (free).
Best Practices for SSL Certificate Management
- Monitor Expiration: Check certificates monthly and renew 30-60 days before
expiration
- Use Automation: Implement automated renewal (e.g., Let's Encrypt with certbot)
- Maintain Inventory: Keep a list of all certificates and their expiration dates
- Set Up Alerts: Configure monitoring to alert you before certificates expire
- Test After Changes: Always verify certificate installation after renewal or updates
- Use Strong Keys: Generate certificates with at least 2048-bit keys
- Keep Private Keys Secure: Never share or expose private keys
- Regular Security Scans: Use our TLS Security Scanner for vulnerability checks
Bulk Certificate Checking
If you manage multiple domains, checking each certificate individually is time-consuming. Use our Bulk SSL Checker to monitor up to
100 domains simultaneously.
Benefits of bulk checking:
- Save time checking multiple certificates
- Get a comprehensive overview of all your certificates
- Identify expiring certificates across your entire infrastructure
- Export results for reporting and compliance
Conclusion
Regular SSL certificate checking is essential for maintaining website security and avoiding downtime.
Whether you use our free online tools, browser features, or command-line utilities, make certificate
monitoring a routine part of your security practices.
Quick Recap:
- Use our SSL Checker for quick, easy
checks
- Check certificates monthly, especially before expiration
- Verify certificate validity, issuer, domain match, and chain
- Use automation for certificate renewal when possible
- Monitor multiple domains with our Bulk Checker