WhatsApp Broadcast at Scale: Lists, Limits and When You Have to Move to the API

Three different things get called broadcasting, and the differences decide whether your message arrives at all.

The three mechanisms#

Broadcast lists (app). Individual messages sent to a list. Recipients reply privately and do not see each other. Free. Reach limited to contacts who saved your number.

Groups. A shared room. Everyone sees everyone's number and messages. Free. Unsuitable as a marketing channel for the obvious reason: your customer list becomes visible to your customers, and one angry reply is broadcast to everyone.

Template campaigns (Business Platform). Approved templates sent through the API to opted-in contacts. Paid per message. No saved-contact requirement, per-recipient delivery reporting, and no manual list handling.

The limits that actually bite#

The saved-contact rule. For broadcast lists only: the recipient must have your number in their phone. There is no setting that changes it, and no error when a recipient is skipped. This is why campaigns "half deliver" — the full diagnosis is in broadcast not delivering to everyone.

List size ceilings. The app caps how many recipients one broadcast list can hold. Splitting into several lists multiplies manual work and creates duplicate-send risk.

Messaging limits (API). Business Platform numbers have a tier that caps how many business-initiated conversations you can start in a rolling window. Tiers step up as your number builds a history of good-quality sending, and step down when quality drops. Plan campaigns around your current tier rather than assuming headroom.

Rate limiting. Sending very large volumes in a burst gets throttled regardless of tier. Stagger.

Exact ceilings change over time — verify against Meta's current documentation before planning a campaign around a number.

Deliverability: why half a list goes unread#

Delivery is not engagement. Even with everything technically correct:

• Numbers churn. Any list older than a year contains dead numbers.
• Some recipients block business numbers on principle after one unwanted send.
• Content that arrives at the wrong hour is read but ignored, and read-then-ignored trains people to ignore the next one.

Cleaning the list is cheaper than sending to it. Remove numbers with no engagement across several campaigns; they cost money per message on the API and damage quality signals.

The move to the API#

You have outgrown the app when any of these is true:

• Your list is bigger than a few hundred contacts.
• You cannot rely on recipients having saved your number.
• More than one person needs to answer the replies — see one number, several agents.
• You need to know who received what.
• You need to send from software rather than from a phone.

What changes: content goes through template approval, sends cost money per message, and the number leaves the consumer app. What you gain: reach independent of saved contacts, delivery states per recipient, segmentation, scheduling and reporting.

The cost question is answered in what WhatsApp messaging actually costs.

A pre-send checklist#

1. Every recipient opted in, with the record to prove it.
2. Numbers in full international format, deduplicated, dead numbers removed.
3. Template approved and tested with a live send to an internal number.
4. Segment chosen deliberately — the smallest audience for whom the message is genuinely relevant.
5. Send window inside sane local hours.
6. Opt-out instruction present, and a process to honour it same-day.
7. Someone staffed to answer replies for the next two hours.
8. Block and opt-out rates checked after the send, and compared with the last campaign.

Point 7 is the one businesses skip. A campaign that generates replies nobody answers converts worse than no campaign, and it costs you the same per message.

Send your first template campaign in AR-Inbox, with segmentation, scheduling and per-recipient delivery states.

Related: why broadcasts do not reach everyone · the marketing playbook.