Digital certificates are stored in files, and those files come in a variety of different formats, both binary and text-based: - The most common binary format is the Distinguished Encoding Rules (*DER*) format. DER certificates are normally stored in files with the .**DER**, .**CRT**, or .**CER** extensions. - The Privacy Enhanced Mail (*PEM*) certificate format is an ASCII text version of the DER format. PEM certificates are normally stored in files with the .**PEM** or .**CRT** extensions - The Personal Information Exchange (*PFX*) format is commonly used by Windows systems. PFX certificates may be stored in binary form, using either .**PFX** or .**P12** file extensions. - Windows systems also use **P7B** certificates, which are stored in ASCII text format. | Standard | Format | File Extensions | | ---------------------------------------- | ------ | ---------------- | | Distinguished Encoding Rules (DER) <br> | Binary | .DER, .CRT, .CER | | Privacy Enhanced Mail (PEM) <br> | Text | .PEM, .CRT | | Personal Information Exchange (PFX) | Binary | .PFX, .P12 | | P7B | Text | .P7B |