Payment Sandbox Helper

A browser extension for developers to quickly generate and auto-fill test card data when working with PayPal Sandbox and Stripe Test environments.

Features

• PayPal Sandbox cards — Generate random valid test cards (Visa, Mastercard, Amex, Diners, Maestro, CUP, JCB) with Luhn-valid numbers
• PayPal error triggers — One-click fill for PayPal-specific error codes (CCREJECT-REFUSED, CCREJECT-SF, etc.)
• Stripe test cards — Full list of Stripe test cards categorized by Success, Decline, and 3DS
• Auto-fill — Automatically fills card number, expiry, CVV, cardholder name, and country into payment forms
• Context menu — Right-click on any input field to fill card data directly
• Customizable settings — Set default country, cardholder name, and card background images
• i18n — Supports English and Vietnamese

Supported Sites

The auto-fill content script runs on:

• *.paypal.com
• *.sandbox.paypal.com
• *.stripe.com
• localhost / 127.0.0.1
• *.appspot.com

Tech Stack

• WXT — Web Extension framework
• React 19 + TypeScript
• Tailwind CSS v4
• FontAwesome icons
• WXT Storage API

Development

# Install dependencies
yarn install

# Dev mode (Chrome)
yarn dev

# Dev mode (Firefox)
yarn dev:firefox

# Build for Chrome
yarn build

# Build for Firefox
yarn build:firefox

# Package as zip
yarn zip
yarn zip:firefox

Project Structure

entrypoints/
  background.ts       # Service worker — sidebar toggle, context menus
  content.ts          # Content script — form detection and auto-fill
  sidepanel/
    App.tsx           # Main UI (PayPal + Stripe tabs, settings)
utils/
  cards.ts            # Card generation helpers (Luhn, random expiry/CVV)
  storage.ts          # WXT storage items (country, cardholder, backgrounds)
public/
  _locales/en/        # English i18n messages
  _locales/vi/        # Vietnamese i18n messages
  img/background/     # Preset card background images

Browser Support

Browser	Status
Chrome	✅ Manifest V3, sidePanel API
Firefox	✅ Manifest V3, sidebar_action API