Affordable WhatsApp AI Chatbot Built with Node.js: Just $6/month

Create a powerful WhatsApp chatbot powered by Google's Gemini AI for just $6/month (WaSenderAPI subscription) plus Google's free Gemini API tier (1500 requests/month).

This Node.js-based solution uses Express.js to handle incoming messages via WaSenderAPI webhooks and leverages Gemini's advanced AI capabilities to generate intelligent, conversational responses.

💰 Cost-Effective Solution

• WaSenderAPI: Only $6/month for WhatsApp integration
• Gemini AI: Free tier with 1500 requests/month
• Hosting: Run locally or on affordable cloud platforms (e.g., Heroku, DigitalOcean)
• No WhatsApp Business API fees: Uses WaSenderAPI as an affordable alternative

🔥 Key Features

• WhatsApp Integration: Receives and sends messages through WaSenderAPI
• AI-Powered Responses: Generates intelligent replies using Google's Gemini AI
• Media Support: Handles text, images, audio, video, and document messages
• Smart Message Splitting: Automatically breaks long responses into multiple messages for better readability
• Customizable AI Persona: Tailor the bot's personality and behavior via simple JSON configuration
• Conversation History: Maintains context between messages for natural conversations
• Robust Error Handling: Detailed logging and error management for reliable operation
• Easy Configuration: Simple setup with environment variables

📁 Project Structure

/whatsapp-nodejs-chatbot/
├── app.js # Main Express application and bot logic
├── package.json # Node.js dependencies and scripts
├── .env # Environment variables (API keys, tokens)
├── persona.json # Customizable AI personality settings
└── README.md # This file

🚀 Setup and Installation

1. Clone the repository

2. Initialize Node.js project and install dependencies:

   npm init -y
   npm install express axios dotenv morgan @google/generative-ai

3. Configure Environment Variables:
   Create a .env file in the project root directory (do not commit this file if it contains sensitive keys):

   GEMINI_API_KEY="YOUR_GEMINI_API_KEY_HERE" # Free tier: 1500 requests/month
   WASENDER_API_TOKEN="YOUR_WASENDER_API_TOKEN_HERE" # $6/month subscription
   PORT=5001 # Optional: default is 5001

   Replace placeholders with your actual API keys.

4. Create or customize persona.json to define your bot’s personality and behavior.

🏃‍♂️ Running the Application

1. Development Mode

Start the Express server locally:

node app.js

The app will listen on http://0.0.0.0:5001/ (or the port set in your .env).

2. Using ngrok for Webhook Testing

WaSenderAPI requires a publicly accessible URL for webhook events. Use ngrok to expose your local server:

ngrok http 5001

Copy the generated public URL (e.g., https://xxxx.ngrok.io) and set your webhook URL in WaSenderAPI dashboard as:

https://xxxx.ngrok.io/webhook

3. Production Deployment

Use a process manager like PM2 or run behind a reverse proxy (Nginx) for production.

Example with PM2:

npm install pm2 -g
pm2 start app.js --name whatsapp-bot

🔄 WaSenderAPI Webhook Configuration

• Log in to your WaSenderAPI dashboard.
• Connect your phone number to a session.
• Set or update the webhook URL to your public endpoint (e.g., ngrok URL or production URL) with /webhook path.
• Enable only the messages.upsert event.
• Save changes.

📝 Customizing Your Bot's Personality

Edit the persona.json file to customize the AI persona and base prompt. For example:

{
"name": "WhatsApp Assistant",
"base_prompt": "You are a helpful and concise AI assistant replying in a WhatsApp chat. Do not use Markdown formatting. Keep your answers short, friendly, and easy to read. If your response is longer than 3 lines, split it into multiple messages using \n every 3 lines. Each \n means a new WhatsApp message. Avoid long paragraphs or unnecessary explanations.",
"description": "You are a friendly WhatsApp assistant. Keep your responses concise and clear."
}

Note: This influences how Gemini AI generates replies.

📊 Logging and Error Handling

• Uses morgan for HTTP request logging.
• Logs detailed info and errors to the console.
• Customize logging as needed for production (file logs, external services).

💡 Why This Solution?

This chatbot offers a cost-effective way to deploy an AI-powered WhatsApp bot without the high costs of WhatsApp Business API. By combining WaSenderAPI's affordable $6/month subscription with Google's free Gemini API tier, you get a powerful, customizable chatbot solution at a fraction of the cost of enterprise alternatives.