WhatsApp is the chat channel, with one rule you cannot ignore
In many markets WhatsApp is where people actually talk, so it is where a business should be reachable. But the platform draws a hard line between replying to a customer and messaging them out of the blue, and the whole design of a WhatsApp integration follows from that line. It is called the 24 hour window.
What the window is
When a user messages you, a 24 hour window opens. Inside it you can reply freely with normal messages. Once it closes, you can no longer send free form text. To reach the user again you must send a pre approved template message, and templates are reviewed by the platform before you are allowed to use them.
The practical consequence
Split your outbound messages into two kinds and treat them differently:
- Inside the window, in response to the user: ordinary session messages, written on the fly.
- Outside the window, business initiated: approved templates only, with the variable parts filled in.
if (withinWindow(lastInboundAt)) {
await sendSessionMessage(to, "Thanks, your ticket is confirmed.");
} else {
await sendTemplate(to, "ticket_confirmation", { name, eventName });
}
If you try to send free text after the window closes, the platform rejects it. Building the check in from the start saves you from discovering the rule in production.
Get your templates approved ahead of time
Templates take time to approve and cannot be edited freely once live, so draft the ones you will need, an order confirmation, an appointment reminder, a payment receipt, and submit them early. Keep the wording clear and avoid anything that reads like marketing spam, because that is what gets a template rejected.
Honour consent
A chat channel that people trust is one that does not abuse the privilege. Message people who asked to hear from you, keep business initiated contact useful rather than promotional, and make opting out easy. The 24 hour window is partly a technical rule and partly the platform enforcing good manners; respecting both is what keeps the channel open to you at all.