# How to add WhatsApp to your SaaS

To add WhatsApp to a SaaS, you connect each customer's own number to Meta's official Cloud API, receive their messages on a webhook and send replies through a REST API. With a gateway such as Nodium this takes five steps and no Meta app of your own.

## The five steps

- **Create an account and an API key.** The key (`nod_…`) drives your whole account.
- **Add each customer as a client** (`POST /tenants`), with your own identifier. See [one key for all your customers](https://nodium.io/en/features/multi-tenant).
- **Send them a connect link.** They connect their own number through Meta's signup, in a few minutes. See [the connect link](https://nodium.io/en/features/embedded-signup).
- **Register one webhook.** Every message your customers' contacts send arrives as `message.received`, signed.
- **Send.** A template to write first, free text to reply within 24 hours.

```bash
# 1. Write first to a customer: on WhatsApp, an approved template
curl https://nodium.io/api/v1/messages \
  -H "Authorization: Bearer $NODIUM_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "channelId": "<channel id>", "to": "+33612345678", "type": "template",
        "templateName": "order_ready", "templateLanguage": "en",
        "variables": { "1": "Karim" }, "idempotencyKey": "order-1042-confirmation" }'

# 2. The customer answers: you receive message.received on your webhook.
#    Reply in free text, within 24 hours:
curl https://nodium.io/api/v1/messages \
  -H "Authorization: Bearer $NODIUM_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "channelId": "<channel id>", "to": "+33612345678", "type": "text",
        "text": "Yes, it is ready.", "idempotencyKey": "order-1042-reply-1" }'
```

## What WhatsApp imposes, whatever the provider

- The [24-hour window](https://nodium.io/en/guides/24-hour-window): free text only within 24 hours of the customer's last message; an approved template otherwise.
- Templates are reviewed by Meta before they can be sent.
- Meta bills its own message fees to the WhatsApp Business account of each number. See [Meta's pricing explained](https://nodium.io/en/guides/meta-pricing).
- A number is on the API or on regular WhatsApp, never both; the WhatsApp Business app can stay, with [coexistence](https://nodium.io/en/features/coexistence).

## Build it yourself, or use a gateway

Calling Meta directly means creating a Meta app, verifying your business, passing app review and becoming a Tech Provider before a single customer can connect, then maintaining tokens, webhooks and Embedded Signup. A gateway holds all of that. See [Tech Provider or Solution Partner](https://nodium.io/en/guides/tech-provider-vs-solution-partner).

## Frequently asked questions

### How long does it take to add WhatsApp to a SaaS?

With a gateway, a first message sent and answered takes an afternoon: an API key, one webhook route and two calls. Connecting each customer then takes them a few minutes, on a hosted page.

### Whose number is it?

Your customer's. They connect a number they own, it stays in their WhatsApp Business account, and they can leave with it.

Updated 2026-11-10 · https://nodium.io/en/guides/add-whatsapp-to-your-saas