SSL & Domain Security Learning Center
Expert guides on SSL certificates, TLS security, DNS, DNSSEC, DMARC, and domain monitoring — written for developers, sysadmins, and security teams.
Featured Guides
Understand how SSL and TLS work, the difference between them, and why every website needs a valid certificate.
A clear technical explanation of the TLS handshake, asymmetric encryption, certificate chains, and OCSP revocation.
Learn how to get and install free, trusted SSL/TLS certificates from Let's Encrypt using Certbot for Apache, Nginx, and more.
Learn why SSL/TLS is mandatory for e-commerce websites, how it helps with PCI DSS compliance, and best practices for securing your online store.
More Articles
A deep dive into what changed between TLS 1.2 and 1.3 — including performance improvements and security enhancements.
Practical steps, automation strategies, and monitoring tools to ensure your SSL certificates never expire unexpectedly.
Understand every certificate type — validation levels, scope, cost, and which one is right for your specific use case.
A detailed comparison of Wildcard and Multi-Domain (SAN) SSL certificates to help you choose the right one for your needs.
Learn how CAs form the backbone of internet trust, how the chain of trust works, and how to choose the right CA.
Learn how DNSSEC works, how to verify it, and why it is critical protection against DNS spoofing and cache poisoning.
Understand what DNS propagation is, why it isn't instantaneous, and how factors like TTL and caching affect the time it takes for DNS changes to go live.
Understand how CT logs work, how to search them for your domain, and how to get alerted when new certs are issued.
From HSTS to certificate pinning — the complete guide to implementing HTTPS correctly and securely.
Complete implementation guide for all major security headers — with Nginx, Apache, and Next.js configuration examples.
Why browsers block mixed content, how to detect it, and step-by-step fixes for WordPress, React, and server configurations.
How to migrate without losing SEO rankings — covering certificates, 301 redirects, HSTS, and post-migration monitoring.
What happens when a domain expires, real-world incidents, and how to set up a reliable multi-channel alert system.
Step-by-step guide covering Certbot, DNS-01 wildcard certs, Kubernetes cert-manager, and cloud-managed certificates.
Integrate certificate health into CI/CD pipelines, Prometheus alerting, Kubernetes, Terraform, and incident runbooks.
Understand how implementing strong SSL/TLS practices helps you meet key requirements of the ISO/IEC 27001 standard for Information Security Management Systems.
Go beyond the basics — COOP, COEP, CORP, Trusted Types, and other advanced isolation headers explained.
Understand HPKP's deprecated legacy, mobile app pinning strategies, and when pinning still makes sense today.
How DANE uses DNSSEC to bind certificates directly to DNS, closing the gap left by the CA trust model.
Step-by-step guide to diagnosing and fixing ERR_SSL_PROTOCOL_ERROR in Chrome and other browsers. Covers TLS mismatches, expired certs, and client-side causes.
Complete guide to Cloudflare Error 526. Understand SSL modes (Full vs Strict), use Cloudflare Origin CA, and permanently fix invalid certificate errors.
Fix Let's Encrypt certificate renewal failures. Troubleshoot ACME challenges, port 80 issues, DNS problems, rate limits, and permission errors.
Five methods to check which TLS version a website supports: OpenSSL, curl, nmap, browser DevTools, and online tools — with examples.
Fix incomplete certificate chain errors. Learn what breaks chain validation, why mobile apps are more sensitive, and how to build a complete chain.
Fix SSL handshake failures. All causes covered: cipher mismatch, TLS version conflicts, certificate validation failures, SNI issues, and firewall interference.
Stop reading about outages. Prevent them.
CertNotify monitors your SSL certificates, domains, and DNS around the clock and alerts you before things break.