SaaS Chrome Extension Django · Python · Gemini AI · Stripe

WhatsBizPro: A Full-Stack WhatsApp Business Platform Built from Scratch

Client: WhatsBizPro · Last updated: April 2026 · Status: Active Production

Project Overview

WhatsBizPro is a production SaaS product — a Chrome extension that supercharges WhatsApp Web with AI-powered response generation, CRM contact management, broadcast messaging, message scheduling, and real-time conversation analysis. It ships with a full Django backend, JWT authentication, Stripe subscription billing, fraud detection, and a bilingual support chat — all built and deployed as a single cohesive product.

This was not a prototype or internal tool — it's a live, monetized product with real subscribers, a 14-day free trial funnel, tiered pricing in USD and MXN, cancellation flows, and webhook-driven subscription lifecycle management. Every line was written from scratch.

Core extension features shipped

Subscription tiers with Stripe billing

Languages supported — EN & ES

The Problem We Solved

WhatsApp is where business happens in Latin America — but WhatsApp Web is a bare-bones messaging interface. Sales teams, service businesses, and solo operators were copy-pasting responses, losing track of leads, manually following up at odd hours, and broadcasting messages one by one. There was no tool that addressed all of this inside WhatsApp itself.

No AI assistance in WhatsApp: Users had to context-switch to a separate AI tool, draft a response, copy it, and paste it back. Every single time.
No CRM in WhatsApp: Contact notes, lead status, custom fields, and business context lived in spreadsheets completely disconnected from the conversation happening right there on screen.
No scheduling: Following up at 9am tomorrow meant either staying up or forgetting entirely. There was no native way to queue a message for a future time.
Broadcast was a manual nightmare: Sending the same promotional or operational message to a list of contacts required opening each chat individually. For 50 contacts that was an hour of work.

What We Built

We delivered a complete SaaS ecosystem — a Chrome extension that lives inside WhatsApp Web, a Django backend that handles auth, AI, subscriptions, and fraud, and a Stripe-powered billing system with full webhook lifecycle management. The product shipped with a freemium model and real paying subscribers on day one.

AI Response Generator: A floating AI button injected into WhatsApp Web's input area. The AI reads the last 10 messages of context, applies the user's custom personality configuration, and generates a natural response in their voice. One click copies it to clipboard — no tab switching, no copy-paste friction.
CRM Side Panel: A full contact management panel that slides in from the right while keeping the WhatsApp chat visible. Standard fields (name, phone, email, address, company, status, tags, notes), custom fields per contact, and global field templates that propagate across all contacts — all stored locally for privacy. Exportable to CSV/Excel.
AI Chat Insights: A side panel that lets users ask natural language questions about the current conversation: "What address did they mention?", "What was the final agreed price?", "What times were discussed?". The AI extracts and surfaces specific data from the full conversation history stored locally.
Broadcast Engine: Select contacts from the WhatsApp sidebar via injected checkboxes, compose a message, and send it to all of them sequentially — the extension handles the search, chat opening, typing, and sending automatically. Built-in 3-second delays between messages to avoid rate limiting.
Message Scheduler: Schedule messages for any future date and time for the currently open contact. The scheduler checks every 30 seconds. When a message is due, it navigates to the contact, types the message, and sends it automatically. If the browser was closed, it shows a popup with the message ready to copy — no silent failures.
Quick Responses: A floating panel anchored to the left edge of the chat column. Users save frequently used messages by name, then copy any of them to clipboard with one click — without opening any panel or navigating away.

Technical Implementation

Extension Architecture: Three-layer Chrome extension — background service worker for auth and stats caching, content scripts injected into WhatsApp Web (AI button, CRM panel, broadcast handler, scheduler, DOM injector), and a popup for stats and navigation. All layers communicate via chrome.runtime messaging.
Backend: Django 5 with Django REST Framework — custom API endpoints for AI generation, chat insights, document analysis, subscription management, and auth. JWT authentication via Simple JWT with access and refresh token rotation. All API responses include CORS headers for WhatsApp Web origin.
AI Engine: Google Gemini 2.5 Flash — used for response generation, chat insights extraction, and PDF document analysis. Each user can upload up to 3 business PDFs; the AI analyzes them to auto-generate a custom personality configuration (communication style, business context, tone) that governs every AI response.
Subscription & Billing: Full Stripe integration — checkout sessions, customer portal, webhook lifecycle handling (subscription.created, subscription.updated, subscription.deleted, invoice.payment_succeeded, invoice.payment_failed), automatic tax, and dual currency pricing (USD/MXN). Cancellation includes a structured feedback form before processing.
Fraud Detection: Custom fraud detection layer that runs on every new subscription — payment method fingerprinting to detect card reuse across accounts, IP address risk scoring, trial abuse detection, and automated fraud alerts for the admin team.
Auth & Security: Email verification flow with account activation tokens, brute-force login protection (rate limiting by IP), honeypot admin panel, JWT blacklisting on logout, and CSRF protection. The extension communicates with the Django backend exclusively over HTTPS with Bearer token authentication.
Email: Resend API for all transactional email — account activation, subscription welcome, cancellation confirmation, reactivation confirmation. All emails sent asynchronously in background threads to keep the request lifecycle fast.

How the Product Works End-to-End

From install to AI-assisted conversation in under 3 minutes:

User installs the Chrome extension and registers on whatsbizpro.org — email verification required. A 14-day free trial starts automatically with trial abuse detection running in the background.
The extension injects its UI into WhatsApp Web — a floating panel, AI button in the input area, Quick Response button on the left edge, and checkboxes on every contact in the sidebar.
The user optionally uploads business PDFs in the extension settings. The Django backend calls Gemini to analyze them and auto-populate the AI personality — communication style, business context, and tone — which shapes all future AI responses.
While chatting, the user hits the AI button. The extension reads the last 10 messages, sends them to the Django AI endpoint with the user's personality config, and displays the generated response above the input area. One click copies it — the user pastes and sends.
At trial end, the user upgrades via the Stripe checkout page. Webhooks fire to update their subscription status in real time. The extension reads the updated status from chrome.storage on every AI request to gate access.

Business Value

A Complete Product, Not a Feature: WhatsBizPro isn't a plugin with one trick — it's a full business productivity suite that lives inside the tool millions of Latin American businesses already use every day. Every feature was designed to eliminate a specific, painful manual process.
Privacy-First Architecture: CRM data lives in the user's browser localStorage — never on our servers. Conversation content is only sent to the AI backend when the user explicitly requests analysis. This isn't just a technical decision — it's the core trust proposition that makes business users comfortable giving the extension access to their WhatsApp.
Monetization Built In From Day One: Free trial → Essentials (free forever) → Pro ($9/month USD or $165/month MXN). Stripe handles billing, the webhook pipeline handles status updates, and the extension gates Pro features with a subscription check on every sensitive request.
Bilingual from the Ground Up: The Chrome extension uses the chrome.i18n API with full EN/ES locale files. The Django backend detects document language (Spanish vs English) and generates AI responses and personality suggestions in the correct language automatically. The landing page and support chat adapt to browser locale.
Fraud Protection That Scales: Trial abuse is the silent killer of freemium SaaS. The fraud detection system fingerprints payment cards, scores IP addresses, tracks trial history, and creates admin alerts — all without adding friction to the legitimate onboarding flow.

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