How can I check if the certificate file I have is in .pem format?

Question

I have a root cert file and I don't know whether or not it is in .pem format. How do I check if it is in .pem format?

Answer 1

DER vs. CRT vs. CER vs. PEM Certificates and How To Convert Them

Quote from the support page:

View ====  Even though PEM encoded certificates are ASCII they are not human readable.  Here are some commands that will let you output the contents of a certificate in human readable form;  View PEM encoded certificate ----------------------------  Use the command that has the extension of your certificate replacing cert.xxx with the name of your certificate  openssl x509 -in cert.pem -text -noout openssl x509 -in cert.cer -text -noout openssl x509 -in cert.crt -text -noout  If you get the folowing error it means that you are trying to view a DER encoded certifciate and need to use the commands in the “View DER encoded certificate  below”  unable to load certificate 12626:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:647:Expecting: TRUSTED CERTIFICATE View DER encoded Certificate   View DER encoded Certificate ----------------------------  openssl x509 -in certificate.der -inform der -text -noout  If you get the following error it means that you are trying to view a PEM encoded certificate with a command meant for DER encoded certs. Use a command in the “View PEM encoded certificate above  unable to load certificate 13978:error:0D0680A8:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag:tasn_dec.c:1306: 13978:error:0D07803A:asn1 encoding routines:ASN1_ITEM_EX_D2I:nested asn1 error:tasn_dec.c:380:Type=X509 

Answer 2

A .pem format certificate will most likely be ASCII-readable. It will have a line -----BEGIN CERTIFICATE-----, followed by base64-encoded data, followed by a line -----END CERTIFICATE-----. There may be other lines before or after.