In detail
The 24-hour customer service window (also called the service window or session window) is the period during which a business can send free-form WhatsApp messages to a customer without using an approved template. It opens the moment a customer sends your business a message and resets to a fresh 24 hours each time they message again.
Inside the window you can reply naturally — plain text, images, documents, interactive buttons — because the customer has just engaged you. This is where "service" messages live: free-form replies within an open conversation. Importantly, "service" is not a template category; the only template categories are Marketing, Utility and Authentication. Service messages are simply what you send inside the window without a template.
Once 24 hours pass with no new customer message, the window closes. To re-open the conversation or proactively reach the customer, you must send an approved message template. Templates are how business-initiated messaging works precisely because there is no open window to reply into.
This structure shapes support and automation design: keep answering promptly while the window is open, and use a Utility or Marketing template (with opt-in) to re-engage after it closes. Many platforms surface a live countdown of the window per conversation so agents know whether a free-form reply is still allowed.
Key points
- Opens when the customer messages you; lasts 24 hours from their last message.
- Inside the window you can reply free-form — no template required.
- "Service" messages are free-form replies in the window, not a template category.
- After it closes, business-initiated messages must use an approved template.
- Each new customer message resets the 24-hour clock.
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