SSL certificate problems are silent killers — your site works fine until one day every visitor sees a red security warning. Here is how to check your certificate before that happens.
Common SSL Certificate Problems
- Expired certificate — The most common issue. Browsers block access entirely.
- Domain mismatch — Certificate issued for www.example.com but site uses example.com.
- Incomplete certificate chain — Missing intermediate certificates cause failures in some browsers.
- Mixed content — Page loads HTTPS but includes HTTP resources.
How to Check Your SSL Certificate
Option 1: SSL Checker Tool
Anonymiz SSL Checker shows certificate details instantly — validity dates, issuer, chain completeness, and days until expiry. Enter any domain and get results in seconds, free.
Option 2: Check in Your Browser
- Visit your site in Chrome or Firefox.
- Click the padlock in the address bar.
- Click Connection is secure then Certificate is valid.
Option 3: OpenSSL Command Line
openssl s_client -connect yourdomain.com:443 | openssl x509 -noout -datesWhen to Check
- Monthly as routine maintenance
- 30 days before expiry — set a calendar reminder
- After server migrations or CDN changes
Why Incomplete Certificate Chains Cause Inconsistent Failures
Your server's certificate is actually signed by an intermediate certificate authority, not directly by the root CA that browsers trust — a complete chain includes both your certificate and that intermediate one, so the browser can trace a path back to a trusted root. If the intermediate is missing, some browsers work anyway because they cache intermediates from other sites they've visited, while others fail immediately, which is exactly why "it works for me but not for my visitors" is such a common and confusing symptom of this specific misconfiguration.
A Renewal Mistake That Catches People Off Guard
Let's Encrypt's auto-renewal via certbot is reliable, but it can silently stop working after a server migration, a firewall change, or a renewal hook script that starts failing — and because certificates are typically issued for 90 days, a break that goes unnoticed has a full three-month runway before it actually causes an outage. Checking that certbot renew --dry-run succeeds periodically, not just assuming auto-renewal is still working, catches this before a certificate actually expires.
How to Renew
For Lets Encrypt: run certbot renew. For paid certificates: renew via your hosting provider. Confirm auto-renewal is enabled.
