Blind carbon copy (abbreviated Bcc) allows the sender of a message to conceal the person entered in the Bcc field from the other recipients. This concept originally applied to paper correspondence and now also applies to email.

In some circumstances, the typist creating a paper correspondence must ensure that multiple recipients of such a document do not see the names of other recipients. To achieve this, the typist can:

• Add the names in a second step to each copy, without carbon paper;
• Set the ribbon not to strike the paper, which leaves names off the top copy (but may leave letter impressions on the paper).

With email, recipients of a message are specified using addresses in any of these three fields:

• To: Primary recipients
• Cc: Carbon copy to secondary recipients—other interested parties
• Bcc: Blind carbon copy to tertiary recipients who receive the message. The primary and secondary recipients cannot see the tertiary recipients. Depending on email software, the tertiary recipients may only see their own email address in Bcc, or they may see the email addresses of all primary and secondary recipients but will not see other tertiary recipients.

It is common practice to use the Bcc: field when addressing a very long list of recipients, or a list of recipients who should not (necessarily) know each other, e.g. in mailing lists.