WhatsApp Template Message vs Session Message: What's the Difference?

A session message is a free-form message a business sends within the 24-hour window that opens whenever a customer messages first - no pre-approval required, since it's treated as a direct reply within an active conversation. That window resets to a fresh 24 hours every time the customer sends another message.

A template message is a pre-approved message format, reviewed and approved by WhatsApp in advance, required for a business to reach out once that 24-hour window has closed - whether to re-engage a customer or to initiate contact in the first place.

The distinction exists entirely because of that 24-hour window. Inside it, a business can respond however it needs to - answering a question, sending an update, having a genuine back-and-forth conversation - without any template restriction, since the customer's own message is what authorized the exchange. Once 24 hours pass since the customer's last message, that authorization expires, and WhatsApp requires a pre-approved template to send anything further, precisely to prevent businesses from messaging people indefinitely without renewed engagement. This means a business that wants to follow up on an order update or re-engage a customer after the window closes needs a template message ready and approved in advance - waiting until the moment it's needed means the conversation simply can't continue until an approved template exists.