Teams moving from the WhatsApp Business app to the WhatsApp Business API often hit the same surprise: a reply that would have gone through on the app is refused on the API. The reason is the 24-hour customer service window. Once you understand it, it becomes a tool rather than an obstacle — and it saves money.
What the window is
Every time a customer sends you a message, a 24-hour customer service window opens for that customer.
Inside the window, you can reply with anything: free text, images, documents, voice notes, location — no template and no approval needed.
When the window closes, free-form messages are no longer allowed. The only way to reach that customer is an approved template message. When the customer replies to it, a new 24-hour window opens.
The window is measured from the customer's latest message. If they message you again, the 24 hours start again.
An example
- Monday 3:00 pm — a customer asks about delivery times. The window opens until Tuesday 3:00 pm.
- Monday 3:10 pm — you reply with details and a photo. Allowed: the window is open.
- Tuesday 11:00 am — you send a follow-up note. Still allowed.
- Tuesday 5:00 pm — you want to share a new offer. The window closed at 3:00 pm, so you need an approved template.
- Tuesday 5:20 pm — the customer replies to your template. A new window opens until Wednesday 5:20 pm.
Why the rule exists
Meta built the API to stop businesses from messaging people who did not expect to hear from them. Inside the window, the customer has just shown they want to talk to you. Outside it, Meta wants every first message to be a pre-approved template, so customers are protected from spam. This rule is Meta's, and it applies on every WhatsApp API platform.
How the window affects cost
Meta charges per template message. Free-form replies inside the open window are not charged as template messages, and utility templates sent inside an open window are also free.
So the same information can cost nothing or something, depending on timing:
- Answering a question within the window: no template charge.
- Answering it the next day: you need a template, which is charged.
Full details are in WhatsApp Business API pricing in India.
What you can do outside the window
You send a template — a message you wrote in advance and Meta approved. Templates can include variables (like the customer's name or order number), media headers and buttons. If you have not set them up yet, plan a few common ones in advance:
- A gentle follow-up: "Hi {{1}}, just checking whether you still need help with your enquiry."
- An order or appointment update.
- A reminder about an unpaid invoice.
Getting templates approved is easier when you know the common mistakes — see why WhatsApp templates get rejected.
Working with the window day to day
- Reply fast. The quicker your team answers, the more of the conversation stays inside the free, flexible window.
- Answer everything in one go. Before the window closes, send the price, photos, address and payment link together rather than waiting for the next question.
- Ask a question at the end. "Shall I book the 5 pm slot for you?" invites a reply, which keeps the conversation open.
- Keep templates ready. For follow-ups after the window closes, an approved template saves time and avoids typing messages that cannot be sent.
- Assign chats. In a shared inbox, a chat nobody owns is a chat whose window quietly expires.
Common questions
Does the window reset if I send a message? No. Only a message from the customer opens or extends the window.
Do customers see the window? No. It only affects what your business is allowed to send.
What about Click-to-WhatsApp ads? When a customer reaches you through a Click-to-WhatsApp ad or a Facebook Page button, Meta opens a 72-hour free entry point window, which gives you longer to continue the conversation at no message charge.
Does the WhatsApp Business app have this rule? No — the rule belongs to the API. That is one of the key differences covered in WhatsApp Business app vs API.
How ONPAD helps
ONPAD's shared inbox shows when a customer's window has closed and offers to send an approved template instead, so your team never writes a reply that cannot be delivered. Conversations can be assigned to a teammate so no window expires unnoticed.
You can try ONPAD free for 7 days or read how the inbox works in the documentation.