Gotchas
Common mistakes and how to fix them
The #1 SSL Mistake: Wrong Certificate Chain Order
Your certificate chain order is probably wrong. Learn why leaf-intermediate-root order matters, how to diagnose chain issues with openssl, and how to fix them in nginx, Apache, and Node.js.
Why Your Certificate Fails Even Though It's Not Expired
Your leaf certificate is valid, but clients reject it anyway. The problem is usually an expired or revoked intermediate certificate, or a cross-signing chain that aged out. Here's how to find and fix it.
Wildcard Certificates: What They Cover and What They Don't
Everything you need to know about wildcard SSL certificates. Covers *.example.com syntax, limitations, multi-level subdomains, security risks, and alternatives like SAN certificates.
Common SSL/TLS Errors and What They Actually Mean
A developer's reference to the most common SSL/TLS error messages. Plain English explanations, real causes, and concrete fixes for ERR_CERT_AUTHORITY_INVALID, ERR_CERT_DATE_INVALID, handshake failures, and more.
Certificate Expiration: Monitoring, Alerts, and Auto-Renewal
How to monitor SSL certificate expiration, set up alerts before certs expire, and automate renewal. Covers openssl checks, Prometheus, cron monitoring, and Let's Encrypt auto-renewal.
Private Key Formats: Why Your Key Gets Rejected
Your private key looks fine but your application won't accept it. The problem is usually a format mismatch between Traditional PEM and PKCS#8. Here's how to tell them apart and convert between them.