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How to convert a .CER certificate to .CRT?

I have bought a certificate for my domain from ComodoSSL. I received the certificate and it has the extension .CER. My provider wants a certificate in .CRT format. How can I convert the .CER to .CRT?

After a long search, I found a quick solution. An SSL certificate is designed to protect the communication between the website and the client. To convert the certificate .CER in .CRT there are few easy steps:

  • Install OpenSSL
  • Setup your environment settings
  • Try if OpenSSL is working in a prompt 

Then, copy your certificate in a folder. Open the prompt directly in this folder. To do that, in the address bar type cmd and then enter. Then type this line (replace www_puresourcecode_com with the name of your certificate):

openssl pkcs7 -print_certs -in .\www_puresourcecode_com.cer -out .\www_puresourcecode_com.crt

OpenSSL in PowerShell

CER vs CRT: The Technical Difference

Fundamentally, there is no difference between CER and CRT… and yet there is a difference between the two. No, we’re not trying to refer to Schrödinger’s cat here, so relax. What we mean is that both are the same SSL certificate format — that is Base64 (ASCII) format — they both are different filename extensions. This is important because a server might require your certificate filename extension to be in either of the two extensions.

Feeling even more confused? Yeah, we thought so. Essentially, these extensions are used for certificates, and they’re encoded in binary DER or as ASCII PEM formats. CER & CRT extensions are most commonly used by the Unix family of operating systems.

X.509 Certificate Filename Extensions
Technically, all SSL certificates are regarded as types of X.509 certificates. These digital certificates have different filename extensions and formats. Here’s a brief overview of several common filename extensions:

  • .pem — This is a (Privacy-enhanced Electronic Mail) Base64 encoded DER certificate, enclosed between “—–BEGIN CERTIFICATE—–” and “—–END CERTIFICATE—–“
  • .cer, .crt, and .der — Although usually in binary DER form, Base64-encoded certificates are also common (see .pem above).
  • .p7b and .p7c — PKCS#7 SignedData structure without data, just certificate(s) or CRL(s).
  • .p12 — PKCS#12 files may contain certificate(s) (public) and private keys (password protected).
  • .pfx — PFX is the predecessor of PKCS#12. This type of file usually contains data in PKCS#12 format (e.g., with PFX files generated in IIS).


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