What is CRT or CER? CRT or CER, short name for Certificate, is used as the file extension for PKI (Public Key Infrastructure) Security Certificate files. .CRT or .CER files are Base64 encoded text files. See the sample .CRT file included below.

File Extension: .CRT

MIME Type: application/x-x509-ca-cert, application/pkix-cert

File Content: Security Certificate

.CRT or .CER files are Security Certificate files. A .CRT or CER file contains a public key digitally signed by a trusted entity. Here is a sample .CRT Security Certificate file containing Yahoo's public key signed by usertrust.com:

-----BEGIN CERTIFICATE-----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...
-----END CERTIFICATE-----

.CRT or CER Security Certificate file sample: Click sample.crt to download.

.CRT or CER files can be created and opened by these software:

• Mozilla Firfox - Creates and opens .CRT or .CER Security Certificate files.
• Internet Explorer - Creates and opens .CRT or .CER Security Certificate files.