Articles & Guides
Useful resources for web developers and system administrators
Found 43 · SSL/TLS · Reset
SSL/TLS
HTTPS Not Working: Local vs Server Causes and How to Fix
HTTPS not working? Check if it fails only for you (clock, antivirus, proxy) or for everyone (certificate, chain, port 443, redirects), then fix it.
SSL/TLS
What Is HTTPS? How It Works and Is the URL Encrypted
HTTPS is HTTP over TLS: the URL path, query, headers and cookies are encrypted; the domain still shows in DNS and SNI. How it works, how to check it.
SSL/TLS
Certbot Renew Not Working: Fix Let's Encrypt Auto-Renewal
Certbot not renewing? Run certbot renew --dry-run, check certbot.timer and renewal configs, HTTP-01 and DNS-01 failures, deploy hooks and rate limits.
SSL/TLS
Cannot Verify Server Certificate or Identity: Causes, Fixes
Cannot verify the server certificate? The name does not match, it is expired or self-signed, the chain is incomplete or revoked, or your clock is wrong.
SSL/TLS
NET::ERR_CERT_AUTHORITY_INVALID: Causes and Exact Fixes
NET::ERR_CERT_AUTHORITY_INVALID means the issuer is untrusted. Find your case in one minute: missing chain, self-signed cert, antivirus, clock, proxy.
SSL/TLS
ERR_SSL_VERSION_OR_CIPHER_MISMATCH: Find the Cause and Fix It
ERR_SSL_VERSION_OR_CIPHER_MISMATCH means no shared TLS version or cipher. openssl tests, nginx, Apache, IIS and Cloudflare fixes, plus old router admin pages.
SSL/TLS
Cloudflare 525 SSL Handshake Failed Fix
Cloudflare error 525 SSL Handshake Failed means the TLS handshake with the origin failed. Check the origin certificate, use openssl s_client, and fix SSL modes.
SSL/TLS
ERR_SSL_PROTOCOL_ERROR Fix
ERR_SSL_PROTOCOL_ERROR is a failed SSL/TLS handshake. Learn the causes, diagnose with openssl and curl, and fix the certificate and protocol step by step.
SSL/TLS
Post-Quantum TLS: What Changes in 2026
Post-quantum TLS defends against harvest-now-decrypt-later attacks. We cover ML-KEM (Kyber, FIPS 203), the X25519MLKEM768 hybrid and the PQC migration in 2026.
SSL/TLS
Russian Trusted Root CA and Sub CA on Servers: Install
Russian Trusted Root CA and Sub CA for engineers: why the TLS chain breaks for servers and scripts, and how to add the root to Linux, Java, Python.