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Once a session is ready and linked to a sender, you send and receive with the same APIs as every other channel — just route on the whatsapp_alt channel.

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Sending

Set channel: "whatsapp_alt" and target the sender that owns the linked session with the Zavu-Sender header (or omit it to use the project default). 
curl -X POST https://api.zavu.dev/v1/messages \
  -H "Authorization: Bearer $ZAVU_API_KEY" \
  -H "Zavu-Sender: sender_12345" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "+14155551234",
    "channel": "whatsapp_alt",
    "text": "Hello from Zavu!"
  }'

const { message } = await zavu.messages.send({
  to: "+14155551234",
  channel: "whatsapp_alt",
  text: "Hello from Zavu!",
}, {
  headers: { "Zavu-Sender": "sender_12345" },
});

resp = zavu.messages.send(
    to="+14155551234",
    channel="whatsapp_alt",
    text="Hello from Zavu!",
    extra_headers={"Zavu-Sender": "sender_12345"},
)
whatsapp_alt is only accepted for teams with the WhatsApp Alternative feature enabled, and the sender must have a connected whatsapp_alt session. Without a linked session the send is rejected.

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Supported message types

WhatsApp Alternative carries conversational content: text, media (image, video, audio, document, sticker), location, contacts, and reactions. It does not use WhatsApp templates or the 24-hour window — those are concepts of the official WhatsApp Business Platform. Media and reactions are sent the same way as the official WhatsApp channel; see the WhatsApp message guides.
Because the number is a QR-linked device, keep to consented, conversational messaging. High-volume or unsolicited sending risks WhatsApp blocking the number. For large marketing sends, use the official WhatsApp channel with approved templates.

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Receiving

Inbound messages arrive through your sender’s webhook as message.inbound events — the same shape as every other channel, so your existing webhook handler works without changes.
Webhook payload
{
  "id": "evt_1736850000000_abc123",
  "type": "message.inbound",
  "timestamp": 1736850000000,
  "senderId": "sender_12345",
  "projectId": "proj_abc",
  "data": {
    "messageId": "jx77...",
    "to": "+13125551212",
    "channel": "whatsapp_alt",
    "status": "received"
  }
}
Subscribe to message.inbound on the sender and verify the signature exactly as documented in Receiving Messages. Delivery and read receipts arrive as message.delivered / message.read for outbound messages. Group messages arrive on the same message.inbound event, with extra group fields on data. See Groups for how to identify a group message and its author.

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Uniform across channels

The value of whatsapp_alt is that it plugs into the same surface as the rest of Zavu:
  • Same send API — only channel changes.
  • Same webhooks — message.inbound, message.delivered, message.read, message.failed.
  • Same contacts and conversations — a linked number’s conversations live alongside your SMS, email, and official WhatsApp threads.

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Next steps

Receiving Messages

Configure and verify your sender webhook.

Egress & Fallback

Keep the linked number 100% active.