If you have .crt file, you can find more details about the certificate with command
openssl x509 -text -noout -in certificate.crt
To get details of SSL installed on a web site, use
openssl s_client -showcerts -connect domain.com:443
If you have .crt file, you can find more details about the certificate with command
openssl x509 -text -noout -in certificate.crt
To get details of SSL installed on a web site, use
openssl s_client -showcerts -connect domain.com:443