How to Fix ERR_SSL_VERSION_OR_CIPHER_MISMATCH in Nginx & Apache

Root Cause of ERR_SSL_VERSION_OR_CIPHER_MISMATCH

Modern browsers require at least TLS 1.2 or TLS 1.3 and reject deprecated protocols (SSL 2.0, SSL 3.0, TLS 1.0, and TLS 1.1) and insecure ciphers (RC4, 3DES, MD5).

If your server is running legacy configurations that disable modern elliptic-curve ciphers (ECDHE), clients will fail to negotiate a handshake.

Recommended Modern Nginx TLS Configuration

# Enable TLS 1.2 and TLS 1.3 only
ssl_protocols TLSv1.2 TLSv1.3;
ssl_prefer_server_ciphers off;

# Modern robust cipher suites
ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384;

# Session caching for high performance
ssl_session_timeout 1d;
ssl_session_cache shared:SSL:10m;
ssl_session_tickets off;