# WhatsApp messaging rules

Source: https://docs.revoplyai.com/get-started/whatsapp-messaging-rules/

> The 24-hour service window, when a template is required, how Meta bills templates, and what a QR-linked number cannot do.

WhatsApp decides what a business may send and when. These rules come from Meta and apply
to every message sent from your number, whether the assistant, your team, a flow or your
system sends it.

## The 24-hour service window [#the-24-hour-service-window]

When a customer writes to your WhatsApp Business number, a 24-hour window opens. Until it
closes, you may send any message: text, media, buttons. Each new message from the customer
restarts the 24 hours.

Outside the window, and to a customer who has never written, you may only send a
**template**. When the REST API is published, a message that is not a template sent
outside the window will be refused with `outside_service_window`.

## Templates [#templates]

A template is a message you submit to Meta for approval in advance, with placeholders for
values such as a name or an order number. Only templates with the status `APPROVED` can be
sent. Meta classifies each one as `MARKETING`, `UTILITY` or `AUTHENTICATION`.

* A flow started by your system ([flow triggers](/flow-triggers/)) must send a template
  before anything else: nobody has written, so no window is open.
* Templates sent by automations count against a daily allowance shared by the account and
  its projects, and at most 3 reach one customer in any 24 hours. See
  [Plans and limits](/get-started/plans-and-limits/).

## Who pays for templates [#who-pays-for-templates]

Meta charges for every template it delivers, at a rate that depends on the template's
category and the recipient's country code. The charge goes to the payment method on your
own WhatsApp Business account, directly from Meta; it is not part of your RevoplyAI bill.

## WhatsApp QR numbers [#whatsapp-qr-numbers]

A number linked by scanning a QR code (`whatsapp_qr`) is not a WhatsApp Business Platform
number:

* it cannot send templates, so it can never start a conversation or reach a customer
  outside a conversation they started;
* flow triggers cannot use it.

See [Channels and capabilities](/get-started/channels-and-capabilities/) for what each
channel can send.

## Opt-outs and quality [#opt-outs-and-quality]

Customers who reply `STOP` are opted out; see
[Opt-out and compliance](/get-started/opt-out-and-compliance/). Customers who block or
report your number lower its quality rating with Meta, which can limit how many
customers it may message a day. Send templates only to customers who expect them.