What Does Blind Carbon Copy (Bcc) Mean?

Mask email recipients from others with a Bcc message

BCC example

A Bcc (blind carbon copy) is a copy of an email message sent to a recipient whose email address does not appear (as a recipient) in the message.

In other words, if you get a blind carbon copy email where the sender put only your email address in the Bcc field, and put their own email in the To field, you will get the email but it will not identify your address in the To field (or any other field) once it hits your email account.

The primary reason people send blind carbon copies is to mask the other recipients from the list of recipients. Using our example again, if the sender bcced multiple people (by putting their addresses in the Bcc field before sending), none of those recipients would see who else the email was sent to.

Note: Bcc is also sometimes spelled BCC (all uppercase), bcced, bcc'd, and bcc:ed.

Bcc vs Cc

Bcc recipients are hidden from the other recipients, which is fundamentally different than To and Cc recipients, whose addresses do appear in the respective header lines.

Every recipient of the message can see all the To and Cc recipients, but only the sender knows about Bcc recipients. If there is more than one Bcc recipient, they do not know about each other either, and they will typically not even see their own address in the email header lines.

The effect of this, in addition to the recipients being hidden, is that unlike regular emails or Cc emails, a "reply all" request from any of the Bcc recipients will not send the message to the other Bcc email addresses.

This is because the other blind carbon copied recipients are unknown to the Bcc recipient.

Note: The underlying internet standard that specifies email format, RFC 5322, is unclear about how hidden Bcc recipients are from each other; it leaves open the possibility that all Bcc recipients get a copy of the message (a message distinct from the copy To and Cc recipients get) where the full Bcc list, including all addresses, is included.

This is highly uncommon, though.

How and When Should I Use Bcc?

Limit your use of Bcc to essentially one case: to protect the privacy of recipients. This might be useful when you send to a group whose members do not know each other or should not be aware of the other recipients.

Other than that, it's best not to use Bcc and instead to add all recipients to the To or Cc fields. Use the To field for people who are direct recipients and the Cc field for people who get a copy for their notice (but who need not themselves take action in response to the email; they're more or less supposed to be a "listener" of the message).

Tip: See How to Use Bcc in Gmail if you're trying to send a blind carbon copy message through your Gmail account. It's supported with other email providers and clients too, like Outlook and iPhone Mail.

How Does Bcc Work?

When an email message is delivered, its recipients are specified independently from the email headers you see as part of the message (the To, Cc and Bcc lines).

If you add Bcc recipients, your email program may take all addresses from the Bcc field combined with the addresses from the To and Cc fields, and specify them as recipients to the mail server it uses to send the message.

While the To and Cc fields are left in place as part of the message header, the email program then removes the Bcc line, however, and it will appear blank to all recipients.

It's also possible for the email program to hand the email server the message headers as you entered them and expect it to deduce Bcc recipients from them. The mail server then will send each of the addresses a copy, but delete the Bcc line itself or at least blank it out.

An Example of a Bcc Email

If the idea behind blind carbon copies is still confusing, consider an example where you're sending an email to your employees...

You want to send an email to Billy, Mary, Jessica, and Zach. The email is regarding where they can go online to find the new work you've assigned to each of them. However, to protect their privacy, none of these people know each other and shouldn't have access to the other people's email addresses or names.

You could send a separate email to each of them, putting Billy's email address in the regular To field, and then doing the same for Mary, Jessica, and Zach. However, that means you have to make four separate emails to send the same thing, which might not be awful for just four people but would be a waste of time for dozens or hundreds.

You can't use the Cc field because that will negate the whole purpose of the blind carbon copy feature.

Instead, you put your own email address in the To field followed by the recipients' email address into the Bcc field so that all four will get the same email.

When Jessica opens her message, she'll see that it came from you but also that it was sent to you (since you put your own email in the To field). She will not, however, see anyone else's email. When Zach opens his, he'll see the same To and From information (your address) but none of the other people's information. The same is true for the other two recipients.

This approach allows for a non-confusing, clean email that has your email address in both the sender and to field. However, you could also make the email appear to be sent to "Undisclosed Recipients" so that each recipient will realize that they weren't the only one who got the email.

See How to Send an Email to Undisclosed Recipients in Outlook for an overview of that, which you can transform to work with your own email client if you don't use Microsoft Outlook.