SSL

Check server certificate with OpenSSL

With SNI

openssl s_client -showcerts -servername www.example.com -connect www.example.com:443 </dev/null

Without SNI

openssl s_client -showcerts -connect www.example.com:443 </dev/null

Full details

echo | \
    openssl s_client -servername www.example.com -connect www.example.com:443 2>/dev/null | \
    openssl x509 -text