To create a broadcast list in WhatsApp, the method differs between the WhatsApp Business App and the WhatsApp Business API.
In the WhatsApp Business App, you must manually add contacts to your phone's contact list, and for them to receive the broadcast, they must also have your number saved in their contacts.
This is a limitation when managing large contact lists. On the other hand, with the WhatsApp Business API, you don't need to save contacts to your phone.
Instead, you can upload and manage your contact lists programmatically via the API, allowing you to send messages to large groups without manually adding them.
However, recipients must have opted in to receive your messages, as WhatsApp requires explicit user consent.