WhatsApp API with n8n: a workflow that receives and replies
To connect the WhatsApp API to n8n, no dedicated node is needed: a Webhook node receives each message from Nodium, and an HTTP Request node replies through the REST API. Add a signature check between the two, so the workflow only runs on events Nodium really sent.
The workflow
- Webhook node — method
POST, with the Raw Body option on: the signature is computed on the body exactly as received. Copy its production URL. - Signature check — the
X-Nodium-Signatureheader ist=<timestamp>,v1=<signature>. With the Crypto node, compute the HMAC-SHA256 of<timestamp>.<raw body>with your webhook secret, in hex, and compare it tov1in an If node. Stop the workflow when they differ. - HTTP Request node — method
POST, URLhttps://nodium.io/api/v1/messages, aBearercredential holding your API key, and the JSON body below.
{ "channelId": "{{ $json.body.data.channel_id }}", "to": "{{ $json.body.data.from }}", "type": "text", "text": "You wrote: {{ $json.body.data.text }}", "idempotencyKey": "reply-{{ $json.body.id }}"}Tell Nodium where to call you
Register the Webhook node's production URL, in the console under Settings › Webhooks or with the call below. The secret is shown once: store it in an n8n credential.
curl https://nodium.io/api/v1/webhooks \ -H "Authorization: Bearer $NODIUM_KEY" \ -H "Content-Type: application/json" \ -d '{ "url": "https://your-app.example.com/webhooks/nodium", "events": ["message.received"] }'# → data.secret (whsec_…): shown onceNext
- The reply above is free text: it only goes out within the 24-hour window. To write first, send a template with
"type": "template". - Keep the
idempotencyKey: when n8n retries a node, the message is sent once. - An AI agent in n8n can also operate WhatsApp through Nodium's MCP server.
Frequently asked questions
Is there an n8n node for Nodium?
No. The Webhook and HTTP Request nodes cover the whole API, which is plain REST.
Can I skip the signature check?
The workflow would run for anyone who finds its URL. Checking the signature is what proves an event comes from Nodium.