openssl x509 -inform

openssl x509 -inform der -noout -text -in /path/to/cerfile.cer 
openssl x509 -inform pem -noout -text -in /path/to/cerfile.cer 

Certificate:
   Data:
       Version: 3 (0x2)
       Serial Number: 0 (0x0)
       Signature Algorithm: sha256WithRSAEncryption
       Issuer: CN = kubernetes
       Validity
           Not Before: Nov 10 19:45:26 2022 GMT
           Not After : Nov  7 19:45:26 2032 GMT
       Subject: CN = kubernetes
       Subject Public Key Info:
           Public Key Algorithm: rsaEncryption
               Public-Key: (2048 bit)
               Modulus:

Related

• x509
• How to check certification expiration date from command line

See also

• openssl x509[ -inform | -text | -dates | -subject | --help]
• X.509, ASN.1, openssl x509, .pem, der, PFX, PKCS, SAN, openssl x509, CSR