WhatsApp coexistence — keeping the app and the API on one number
In short
Coexistence lets one phone number work in the WhatsApp Business app and on the WhatsApp Business Platform at the same time. The owner keeps answering from their phone, software can see those conversations and broadcast to the list, and up to six months of chat history is copied across when it is connected. The number is never registered or deregistered, so nothing is taken off the phone. Coexistence numbers are capped at 20 messages per second, and two webhook subscriptions must be enabled or the software sees only half of each conversation.
Checked
The old choice was brutal: move your number to the API and lose the WhatsApp Business app on it, or keep the app and never broadcast to more than 256 people. Coexistence removes the choice. One number, both things, at once.
What it actually does
The owner keeps the WhatsApp Business app on their phone and uses it exactly as before. Nothing moves. Alongside it, software connects to the same number through the WhatsApp Business Platform and can:
- see incoming messages from customers;
- see the messages the owner sends from the phone, so the shared inbox shows the whole conversation rather than half of it;
- send broadcasts to a list of any size;
- send automated replies and order updates.
This is the normal onboarding path for small businesses now, not an exotic option.
The history
When the number is connected, Meta backfills up to six months of chat history. The inbox is not empty on day one, and an agent can see what a customer was told in March. Two things about it are worth knowing first.
A backfilled message is not news. A conversation from March should not raise an unread badge today, and it does not open a 24-hour window that closed in the spring. Software treating backfilled messages as new arrivals produces a screen full of false urgency on the first morning.
History is not consent. People in that backfill wrote to the business before any of this existed. That is a reason you may reply to them, not an opt-in record, and not permission to broadcast to them. What actually counts as opt-in.
The two subscriptions nobody mentions
Meta reports a coexistence conversation through two webhook subscriptions, and both have to be switched on in the Meta app dashboard. No software can enable them for you.
history— the one-time backfill of up to six months.smb_message_echoes— every message the owner sends from the app afterwards.
Without the second, the inbox shows what the customer said and not what the owner replied. An agent who cannot see that the owner answered twenty minutes ago answers again, and the customer gets two different responses from one business. If your inbox shows half of each conversation, this is why.
The speed cap
A coexistence number sends at 20 messages per second, fixed; a fully registered number can go faster once Meta raises its throughput. For most lists this is irrelevant — 20 per second is 72,000 an hour. It matters when you are sending hundreds of thousands inside a narrow window.
The rule that protects you
A coexistence number must never be registered or deregistered. Registering it pulls the number off the owner’s WhatsApp Business app and takes the chat history with it — the exact outcome coexistence exists to prevent, and not reversible in any comfortable way.
A coexistence number arrives already able to send. If any tool or support agent proposes registering it, or setting a two-step PIN on it, as a troubleshooting step, stop and ask why. That step is how businesses lose their WhatsApp.
What to check before you connect
- Is the number on the WhatsApp Business app, and does the owner want to keep using it? Then coexistence is what you want.
- Have both webhook subscriptions been enabled in the Meta app dashboard?
- Does the tool distinguish backfilled messages from new ones?
- Does it treat backfilled contacts as opted-in? It should not — they should land as unknown and stay out of marketing until they opt in properly.
