Send a WhatsApp message with the API

This guide shows two ways to send a WhatsApp message with open-wa. Use the Node.js library when your application runs in Node.js or Bun. Use the Easy API when your application uses another language or runs on a different machine.

The two paths use a WhatsApp account that you link to your own server. open-wa is not the official WhatsApp Business Platform. It connects through WhatsApp Web.

Before you startCopy Anchor Link

• Install Node.js 22 or later.
• Keep a phone with WhatsApp near you to link the account.
• Get the phone number of a test recipient that already has a chat with your account.

To start a chat with a new number, you must apply a Restricted or Insiders license. A recipient with an existing chat does not need a license. See licensed features.

Find the recipient chat IDCopy Anchor Link

open-wa sends to a chat ID, not to a plain phone number. For a person, write the full international number without +, spaces, or dashes. Then add @c.us to the end.

If an incoming message gives a message.from value, use that value without changes. It can end in @lid. Read the chat ID primer for all ID types.

Send from Node.jsCopy Anchor Link

Install the library in your project:

npm install @open-wa/wa-automate

Create send.mts with this code:

import { create } from '@open-wa/wa-automate';

const client = await create({ sessionId: 'sender' });

const messageId = await client.sendText('447123456789@c.us', 'Hello from open-wa');
console.log('Submitted message', messageId);

await client.stop();

Run the file. On the first run, scan the QR code with WhatsApp on your phone. open-wa keeps the login for the next run.

npx tsx send.mts

sendText returns a serialized message ID when WhatsApp accepts the message. The ID confirms submission. It does not confirm delivery. To monitor delivery, subscribe to onAck before you send. See acknowledgements.

Send through the HTTP APICopy Anchor Link

Start the Easy API on the machine that holds the WhatsApp session:

npx @open-wa/wa-automate --session-id sender --host 127.0.0.1 --port 8080 --api-key "your-api-key"

Scan the QR code that the terminal shows. Then send a POST request to /api/messages/sendText:

curl -X POST http://localhost:8080/api/messages/sendText \
  -H "Content-Type: application/json" \
  -H "X-API-Key: your-api-key" \
  -d '{"to":"447123456789@c.us","content":"Hello from open-wa","options":{}}'

A successful response has success: true. The data value is the send result.

{
  "success": true,
  "data": "<runtime-dependent send result>"
}

The same request works from any language that can send HTTP requests. This example uses Python with requests:

import requests

response = requests.post(
    "http://localhost:8080/api/messages/sendText",
    headers={"X-API-Key": "your-api-key"},
    json={"to": "447123456789@c.us", "content": "Hello from open-wa", "options": {}},
    timeout=30,
)
response.raise_for_status()
print(response.json())

The Easy API also serves interactive API docs at http://localhost:8080/api-docs/. Use these docs to find the request body for each method.

Reply to a received messageCopy Anchor Link

To reply in the same chat, use the sender chat ID from the incoming message. To quote the message, give its ID to reply.

client.onMessage(async (message) => {
  if (message.body === 'ping') {
    await client.reply(message.from, 'pong', message.id);
  }
});

For a complete bot, read build a WhatsApp bot.

TroubleshootingCopy Anchor Link

RelatedCopy Anchor Link

• Messages and message events
• WhatsApp webhooks
• Quick start
• Client API reference