How to Use whatsmeow-node with n8n

n8n is a self-hosted workflow automation platform — like Zapier, but open source. Its built-in WhatsApp node requires the official Cloud API (Meta Business verification, per-message pricing). With whatsmeow-node, you can connect n8n to WhatsApp for free using a simple REST bridge.

How It Works

n8n Workflow
  ↕ HTTP requests / webhooks
whatsmeow-node REST API (Express)
  ↕
WhatsApp

Receiving: whatsmeow-node gets a WhatsApp message → POSTs it to an n8n webhook
Sending: n8n workflow makes an HTTP request → whatsmeow-node REST API sends the message

Prerequisites

A paired whatsmeow-node session (How to Pair)
n8n running (self-hosted or cloud) — npx n8n for a quick start
Express: npm install express

Step 1: Create the whatsmeow-node REST API

This server does two things: sends messages via REST and forwards incoming messages to n8n.

import { createClient } from "@whatsmeow-node/whatsmeow-node";
import express from "express";

const client = createClient({ store: "session.db" });
const app = express();
app.use(express.json());

// n8n webhook URL — you'll set this up in Step 3
const N8N_WEBHOOK_URL = process.env.N8N_WEBHOOK_URL ?? "http://localhost:5678/webhook/whatsapp";

// --- Sending endpoint (n8n calls this) ---
app.post("/api/send", async (req, res) => {
  const { phone, message, groupJid } = req.body;
  const jid = groupJid ?? `${phone}@s.whatsapp.net`;

  try {
    const resp = await client.sendMessage(jid, { conversation: message });
    res.json({ sent: true, id: resp.id });
  } catch (err) {
    res.status(500).json({ error: "Failed to send" });
  }
});

// --- Forward incoming messages to n8n ---
client.on("message", async ({ info, message }) => {
  if (info.isFromMe) return;

  const text =
    (message.conversation as string) ??
    (message.extendedTextMessage as { text?: string } | undefined)?.text;

  // POST to n8n webhook
  try {
    await fetch(N8N_WEBHOOK_URL, {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({
        from: info.sender,
        chat: info.chat,
        pushName: info.pushName,
        messageId: info.id,
        text: text ?? null,
        isGroup: info.isGroup,
        timestamp: info.timestamp,
        hasMedia: !!(
          message.imageMessage ??
          message.videoMessage ??
          message.audioMessage ??
          message.documentMessage
        ),
      }),
    });
  } catch (err) {
    console.error("Failed to forward to n8n:", err);
  }
});

async function main() {
  const { jid } = await client.init();
  if (!jid) {
    console.error("Not paired!");
    process.exit(1);
  }
  await client.connect();
  app.listen(3000, () => console.log("WhatsApp API on :3000"));
}

main().catch(console.error);

Step 2: Set Up the n8n Webhook Trigger

In n8n, create a new workflow:

Add a Webhook node as the trigger
Set method to POST
Set path to whatsapp (makes the URL http://localhost:5678/webhook/whatsapp)
Set the webhook URL as N8N_WEBHOOK_URL in your REST API environment

Now every incoming WhatsApp message triggers this n8n workflow.

Step 3: Send Messages from n8n

Add an HTTP Request node to your n8n workflow:

Method: POST
URL: http://localhost:3000/api/send
Body (JSON):

{
  "phone": "{{ $json.from.replace('@s.whatsapp.net', '') }}",
  "message": "Thanks for your message! We'll get back to you soon."
}

Example: Auto-Reply Workflow

A complete n8n workflow that auto-replies to messages:

[Webhook Trigger] → [IF: text contains "price"] → [HTTP Request: send reply]
                  → [IF: text contains "help"]  → [HTTP Request: send help menu]
                  → [Default]                    → [HTTP Request: send acknowledgment]

Example: CRM Integration

Forward WhatsApp messages to a CRM and reply with the ticket number:

[Webhook Trigger] → [HTTP Request: create CRM ticket]
                  → [Set: extract ticket ID]
                  → [HTTP Request: send "Your ticket #{{ ticketId }} has been created"]

Example: AI-Powered Auto-Reply

Combine with OpenAI in n8n:

[Webhook Trigger] → [OpenAI Chat: generate reply]
                  → [HTTP Request: send AI reply via whatsmeow-node]

Adding More Endpoints

Extend the REST API for n8n workflows that need more features:

// Send media
app.post("/api/send-media", async (req, res) => {
  const { phone, filePath, mediaType, caption } = req.body;
  const jid = `${phone}@s.whatsapp.net`;
  const media = await client.uploadMedia(filePath, mediaType);
  await client.sendRawMessage(jid, {
    [`${mediaType}Message`]: {
      URL: media.URL,
      directPath: media.directPath,
      mediaKey: media.mediaKey,
      fileEncSHA256: media.fileEncSHA256,
      fileSHA256: media.fileSHA256,
      fileLength: String(media.fileLength),
      mimetype: `${mediaType}/*`,
      ...(caption && { caption }),
    },
  });
  res.json({ sent: true });
});

// Send to group
app.post("/api/send-group", async (req, res) => {
  const { groupJid, message } = req.body;
  const resp = await client.sendMessage(groupJid, { conversation: message });
  res.json({ sent: true, id: resp.id });
});

// Mark as read
app.post("/api/read", async (req, res) => {
  const { messageId, chat, sender } = req.body;
  await client.markRead([messageId], chat, sender);
  res.json({ ok: true });
});

Common Pitfalls

Keep both services running

The whatsmeow-node REST API and n8n must both be running. Use PM2 or Docker Compose to manage them together.

Webhook URL must be reachable

n8n's webhook URL must be accessible from the whatsmeow-node server. In Docker, use the container name or network alias, not localhost.

Rate limiting

n8n workflows can execute very fast. If your workflow sends multiple messages, add a Wait node (1-3 seconds) between sends to avoid WhatsApp rate limiting.