# The WhatsApp customer service window

WhatsApp does not let a business message whoever it likes whenever it likes. What you are allowed to send depends on whether a conversation is open, and Meta calls that open period the [customer service window](https://developers.facebook.com/documentation/business-messaging/whatsapp/messages/send-messages#customer-service-windows).

## When the window opens and closes

The window opens when a WhatsApp user messages you or [calls you](https://developers.facebook.com/documentation/business-messaging/whatsapp/calling/pricing#how-calling-changes-the-24-hour-customer-service-window), and it runs for 24 hours. Every new message or call from that same user resets it to a fresh 24 hours, so an active back-and-forth keeps the window open indefinitely.

While it is open, you can send free-form content: text, images, documents, and the other message types Meta allows in a live conversation. Nothing needs prior approval, because the customer started the exchange. Meta calls these service messages, and charges nothing for them: non-template messages inside an open window are free, as are utility templates delivered inside one ([WhatsApp pricing](https://developers.facebook.com/documentation/business-messaging/whatsapp/pricing)).

When it closes, free-form content stops reaching that person. An approved template is the only thing that does.

Nothing you send opens a window on its own terms. A template you send to someone who has not written to you starts a business-initiated conversation, and it still needs the [opt-in](https://developers.facebook.com/documentation/business-messaging/whatsapp/getting-opt-in) Meta requires before you message anyone.

Meta also documents a [known issue](https://developers.facebook.com/documentation/business-messaging/whatsapp/messages/send-messages#customer-service-windows): in rare cases a message arrives from a user and you cannot reply inside the window it should have opened.

## Why the rule exists

It puts the customer in control of who talks to them. A business can always answer a question it was asked, and cannot use that answer as a door into unsolicited messaging a week later. The template requirement outside the window is what makes the difference enforceable: every business-initiated message has passed Meta's review before it is sent.

For your side of the exchange, this is also a service-level expectation. A question that sits unanswered for more than a day cannot be answered in the same conversation at all.

## What this means on Bird

Whatever you send first is a template, which is the shape the window requires anyway: it has already been approved. Free-form content inside an open window needs a [number of your own](/docs/guides/whatsapp/phone-number-setup), because Bird's shared numbers carry managed templates only.

Bird does not track the window for you. A free-form send outside one is accepted and then fails, with `service_window_expired` on the message. [Sending WhatsApp messages](/docs/guides/whatsapp/sending-whatsapp) covers both content kinds, and [WhatsApp templates](/docs/guides/whatsapp/templates) the templates available to you.

Time in the window is worth watching for anything conversational. If a customer's question comes in and the reply depends on a human, the clock started when their message arrived, not when someone picked it up.

## Next steps

- [WhatsApp sending FAQ](/docs/knowledge-base/faq/whatsapp-sending): the questions this one raises next
- [WhatsApp template guidelines](/docs/knowledge-base/whatsapp/template-guidelines): what Meta allows in the template you send outside the window
- [WhatsApp business verification](/docs/knowledge-base/whatsapp/business-verification): the limits on how many conversations you can start
- Meta's own reference: [Customer service windows](https://developers.facebook.com/documentation/business-messaging/whatsapp/messages/send-messages#customer-service-windows) and [Pricing](https://developers.facebook.com/documentation/business-messaging/whatsapp/pricing)