When you connect a WhatsApp Business number to a platform like ours, Meta gives you two paths, and the choice is permanent for that number until you actively change it again.
Full Cloud API migration moves the number entirely onto the Cloud API. You get the highest throughput available, with no artificial rate cap from Meta's side. The tradeoff is that the WhatsApp Business mobile app stops working for that number the moment migration completes — you can't scan a QR code to bring it back onto your phone without going through a separate re-registration process later.
Coexistence keeps the WhatsApp Business app usable on your phone at the same time the Cloud API is active, syncing messages in both directions through webhook events (message echoes and a one-time history sync of your recent chats). The tradeoff here is throughput: Meta caps Coexistence-connected numbers at roughly 5 messages per second, which is fine for most small and medium businesses but can matter if you run large broadcasts.
There's no universally correct answer. A business that has staff physically replying from a phone, or that isn't ready to give up the familiar app, should pick Coexistence. A business running high-volume automated messaging with no one checking a physical phone should pick Full Migration. If you're not sure, Coexistence is the safer default — it's reversible in spirit (you keep your existing workflow as a fallback) in a way Full Migration is not.
Whichever you pick, the one-click "Continue with Facebook" flow in the Setup Guide handles the actual registration with Meta — you just choose the mode first.