Trial Guard - Chrome Trial Reminder SaaS Kit

Trial Guard is a production-ready Manifest V3 Chrome Extension and turnkey Micro-SaaS starter kit designed to help developers and entrepreneurs launch their own browser-tool business in minutes.

The extension automatically detects free-trial offers on websites and prompts users to schedule a pre-filled Google Calendar reminder before recurring subscription charges occur. With built-in freemium logic and automated Whop licensing, this package is completely monetization-ready out of the box.

The Business Opportunity

Subscription fatigue is at an all-time high. Users constantly sign up for software trials and forget to cancel before getting billed. Trial Guard solves this painful problem directly inside the browser. As the owner of this codebase, you can rebrand the extension, publish it under your own brand on the Chrome Web Store, and charge a monthly subscription fee using the included Whop license integration.

How It Works & Architecture

• Dual-Engine Detection: High-precision local regex instantly scans buttons and pricing cards. For complex or unstructured pages, it securely queries a serverless Cloudflare Worker powered by Google Gemini AI.
• 1-Click Calendar Scheduling: Opens an instant Google Calendar event template pre-filled with the service name and cancellation lead time—requiring zero complicated Google OAuth scopes.
• Freemium & Licensing Gate: Free users receive a configurable monthly reminder allowance (default: 10). Upgrading to Pro unlocks unlimited reminders, verified securely against Whop’s API.
• Privacy & Store Compliance: Strictly ignores payment fields, checkout URLs, and banking inputs. All snippets are automatically redacted of personal data before leaving the browser.

What’s Included in the Download:

• Complete Manifest V3 Chrome Extension source code (HTML, CSS, JS)
• Cloudflare Worker serverless backend (worker.js + wrangler.toml)
• One-command brand customizer script (stamp-brand.mjs)
• Automated broken-link checking script for cancellation URLs
• Unit test suite for detection patterns and worker endpoints
• Step-by-step HTML and PDF setup documentation with screenshots

Features

• Latest Manifest V3 Architecture: Built strictly according to modern Chrome Web Store security and privacy standards.
• Smart Dual-Engine Detection: Instant client-side regex engine paired with serverless Gemini AI fallback for unstructured web pages.
• 1-Click Google Calendar Integration: Generates instant pre-filled event templates without requiring complicated OAuth approvals.
• Built-in Freemium Logic: Includes local monthly reminder counters and upgrade prompts to easily convert free users into paying subscribers.
• Automated Whop Licensing: Serverless license validation with hardware/device binding to prevent license sharing.
• Direct Cancellation Directory: Built-in deep links to cancellation and account management pages for 25+ popular platforms.
• Privacy & Safety Safeguards: Automatically excludes checkout forms, card fields, and sensitive pages; redacts emails and numbers before transmission.
• Serverless Cloudflare Worker: Scalable backend that proxies AI requests and licensing checks with built-in rate-limiting.
• One-Command Rebranding: Automated script updates names, badges, and titles across all extension files instantly.
• Comprehensive Documentation: Includes complete step-by-step setup instructions in both responsive HTML and PDF formats.

Requirements

• Web Browser: Google Chrome, Brave, Microsoft Edge, or any Chromium-based browser (minimum version 116+).
• Node.js: Node.js (v18.x or newer recommended) installed on your system to run the branding scripts and Cloudflare CLI.
• Cloudflare Account: Free Cloudflare account to deploy the serverless backend worker.
• Google Gemini API Key: Free Google AI Studio API key (optional, used for AI trial detection fallback).
• Whop Account: Free Whop merchant account (optional, only required if you want to sell Pro license keys).
• Code Editor: Any modern code editor such as VS Code, Cursor, or Sublime Text.

Instructions

• Step 1: Extract the Package: Unzip the downloaded file on your computer to view the extension, backend-worker, and documentation folders.
• Step 2: Deploy Backend Worker: Open your terminal in the backend-worker directory, log in via Wrangler (npx wrangler login), configure your secrets, and deploy with npx wrangler deploy.
• Step 3: Configure the Extension: Open extension/config.js and paste your deployed Cloudflare Worker URL into WORKER_BASE_URL, plus your Whop checkout link into CHECKOUT_URL.
• Step 4: Load Unpacked in Chrome: Open Chrome and navigate to chrome://extensions, turn on Developer mode (top-right toggle), click Load unpacked, and select the extension/ folder.
• Step 5: Test & Rebrand: Test the extension on any pricing/trial webpage. Run node scripts/stamp-brand.mjs to customize branding across all files before publishing to the Chrome Web Store.
• Full Guide: Detailed visual step-by-step instructions are available in the included documentation/index.html and documentation.pdf files.