Cons: Requires a developer or a third-party solution provider (WhatsApp Business Solution Provider - BSP), involves costs (per conversation fees), requires pre-approved message templates for outbound communication after 24 hours of inactivity.
Recommendation: If you plan serious marketing or customer service, invest in the API.
This is where you actively collect numbers with consent.
Your Website or App:
Registration/Checkout Forms: Add a clear, un-ticked checkbox: "Yes, I'd like to receive [types of messages, e.g., order updates, promotions] via WhatsApp."
Dedicated Landing Pages: Create a specific page inviting users to join your WhatsApp list for exclusive content, early access, or special deals.
Pop-ups/Banners: Use non-intrusive pop-ups on relevant pages offering a clear value proposition for joining your WhatsApp list.
Social Media (Facebook, Instagram, LinkedIn, etc.):
Click-to-WhatsApp Ads: Run whatsapp number list paid ads that directly lead users to a pre-filled WhatsApp chat message. Once they send it, they've initiated contact, and you can then ask for explicit opt-in for future marketing.
Organic Posts: Share compelling content and include a "Click here to join our WhatsApp community!" or "Message us on WhatsApp for exclusive deals!" CTA.
Email Marketing:
Include a strong call-to-action in your email newsletters or automated sequences, inviting subscribers to join your WhatsApp list for real-time updates.
Offline Channels (Physical Stores, Events in Dhaka, Chittagong, etc.).