Requires mutual saving:

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a select group of people simultaneously (e.g., event invitations, personal announcements, small business updates to a loyal customer segment).
Limitations:
This is the biggest limitation for whatsapp number list marketing purposes.
Not for spam: WhatsApp actively monitors for spam. Sending unsolicited messages to large groups, even via Broadcast Lists, can lead to your account being flagged or banned.
Limited functionality: It's a simple one-way broadcast; no advanced features like scheduling or deep analytics.
4. WhatsApp Business Contact Management (For Companies)
For businesses, managing contacts on WhatsApp is more structured, especially when using the WhatsApp Business API.

WhatsApp Business App: Small businesses use this app. They build their "contact list" by encouraging customers to initiate conversations or save their business number. They can then use the Broadcast List feature (with the mutual saving limitation) or directly message individual customers who have opted in.
WhatsApp Business API: Larger businesses integrate with the API through official Business Solution Providers (BSPs).
No direct "list" within WhatsApp itself: Companies using the API manage their customer data (including WhatsApp numbers) within their own CRM systems.
Opt-in is mandatory: Businesses must obtain explicit consent from users to send them messages on WhatsApp. This opt-in process typically happens outside of WhatsApp (e.g., on a website, through an app, at point of sale).
Message Templates: For business-initiated messages, pre-approved message templates are required to ensure quality and prevent spam.
Session Messages: Businesses can send free-form "session messages" within 24 hours of a user-initiated conversation.