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.cer file extension

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Certificate file. A security certificate.

Security certificates have a number of different roles. Typically they are used as part of the process of providing secure access to a website (i.e. https), in which case the certificate is generally provided by a trusted third party. It is also possible for a website to generate its own certificate in which case it is said to be self certificated, but these are uncommon because as a user would see a configuration dialog because the certificate would not then be from a trusted source.

Certificates are also used by the EFS recovery agent to enable a trusted account to be able to recover encrypted files.

Security certificates can have different file formats, but the following formats are widely supported:

  • DER encoded binary X.509
  • Base-64 encoded X.509

cf .crt, .der

Can you add to this? Do you know of any applications not already listed which will work with .cer files, view .cer files or open .cer files? Are you able to contribute any additional reference information or file format information about .cer files or have you spotted any errors or omissions? If so please let us know by emailing us at feedback@cryer.co.uk - Thank you.