Using the Broadcast Message feature
We work hard to give you many options for chatting with friends, family and colleagues. The Broadcast feature lets you send a message to many people at once, without revealing the recipients to one another. In this sense, it works like bcc (blind carbon copy) on your email. Each recipient then has the option to respond to you individually.
To further enrich this feature, you can also create Broadcast Lists. These allow you to preserve a saved list of contacts to whom you send Broadcast Messages. In order to be able to send a Broadcast Message to a specific contact, that person must have your phone number saved in their address book. We work hard to curb spam in WhatsApp so that everyone has a positive messaging experience.
WhatsApp Support Team