An expired SSL certificate is one of the most preventable — yet most common — causes of website outages. When your certificate expires, every visitor sees a full-page browser warning that your site is unsafe. Most won't proceed.
What Happens When Your SSL Expires
When an SSL certificate expires:
- Browsers block access: Chrome, Firefox, and Safari show a full-page "Your connection is not private" warning. Most users immediately leave.
- APIs break: Any service calling your HTTPS endpoints will fail with certificate errors.
- Email delivery fails: If your mail server uses the same certificate, outgoing and incoming email stops working.
- SEO takes a hit: Google may temporarily deindex pages that return certificate errors.
Why Certificates Still Expire
You might think, "I use Let's Encrypt with auto-renewal, so I'm fine." In practice, auto-renewal fails more often than people realize:
- DNS changes break HTTP-01 challenges
- Server migrations leave old renewal configs behind
- Firewall rules block the ACME validation requests
- Certbot crashes or runs out of disk space silently
- Paid certificates require manual renewal with your CA
What to Monitor
Good SSL monitoring tracks more than just expiry dates:
- Days until expiry — Get warned at 30, 14, and 7 days before expiration
- Certificate issuer — Detect unexpected issuer changes (potential compromise)
- Protocol version — Ensure you're using TLS 1.2 or 1.3, not deprecated versions
- Certificate chain — Verify the full chain is valid and trusted
Setting Up SSL Monitoring with WebMon
WebMon automatically monitors SSL certificates for every HTTPS monitor you add:
- Add your website as an HTTP monitor
- WebMon checks the SSL certificate on every monitoring cycle
- You receive alerts when the certificate is within 30, 14, or 7 days of expiry
- Certificate details (issuer, protocol, expiry date) are visible on your monitor dashboard
There's no extra configuration needed — SSL monitoring is included automatically with every HTTP monitor.
Best Practices
- Monitor all your domains — Don't forget subdomains, staging environments, and API endpoints
- Set expiry alerts early — 30 days gives you time to renew without panic
- Monitor certificate changes — An unexpected issuer change could indicate a man-in-the-middle attack
- Test after renewal — Always verify the new certificate is properly installed
SSL monitoring is a simple safeguard that prevents one of the most embarrassing and costly website failures. Set it up once and never worry about expired certificates again.