You can run this to get details about the certificate chain: $ SITE=en.greatfire.org $ echo "HEAD / HTTP/1.0\n Host: $SITE:443\n\n EOT\n" | openssl s_c

You can run this to get details about the certificate chain: $ SITE=en.greatfire.org $ echo "HEAD / HTTP/1.0\n Host: $SITE:443\n\n EOT\n" | openssl s_client -prexit -connect $SITE:443 I'm not sure how to interpret the results, but I'd be thrilled if someone more knowledgeable would comment. I see there is this chain of certs: Certificate chain 0 s:/OU=Domain Control Validated/OU=PositiveSSL/CN=greatfire.org i:/C=GB/ST=Greater Manchester/L=Salford/O=COMODO CA Limited/CN=PositiveSSL CA 2 1 s:/C=SE/O=AddTrust AB/OU=AddTrust External TTP Network/CN=AddTrust External CA Root i:/C=SE/O=AddTrust AB/OU=AddTrust External TTP Network/CN=AddTrust External CA Root 2 s:/C=GB/ST=Greater Manchester/L=Salford/O=COMODO CA Limited/CN=PositiveSSL CA 2 i:/C=SE/O=AddTrust AB/OU=AddTrust External TTP Network/CN=AddTrust External CA Root and openssl seems to complain about a self-signed certificate: Verify return code: 19 (self signed certificate in certificate chain)