24-Hour Window (WhatsApp)
The period after a customer messages you when you may reply with free-form content; outside it, only templates.
The 24-Hour Window is WhatsApp's rule that you may send free-form messages (any text, images, buttons) for 24 hours after a customer last messaged you. Once it closes, you may only start a conversation with a pre-approved template. Understanding this window is key to both compliance and controlling WhatsApp costs.