GreenLight

Know exactly when all the math turns green.

Free, privacy-first financial planning tool that runs entirely in your browser. No account. No backend. No data leaves your device.

What It Does

• Track your complete financial picture: stocks, crypto, cash, and retirement accounts
• Accurate tax estimates using progressive federal brackets for all 50 states + DC
• Plan major purchases (home or vehicle) with detailed cost breakdowns
• Compare mortgage lenders with opportunity-cost-adjusted break-even analysis
• Project when you'll be financially ready for a purchase
• Import directly from ComputerShare, Gemini, Fidelity, and Transamerica

Quick Start

Prerequisites

• Node.js 20+
• npm 9+

Run Locally

git clone https://github.com/NimbleEngineer21/greenlight.git
cd greenlight
npm install
npm run dev
# Open http://localhost:5173

Docker

docker build -t greenlight .
docker run -p 8080:80 greenlight
# Open http://localhost:8080

Privacy First

GreenLight stores all data in your browser — nothing is ever sent to a server:

Storage	What's stored
localStorage	App state: assets, tax config, purchase plan, settings
IndexedDB (via Dexie)	Price history cache, time-series data

• No account required
• No analytics, no tracking, no cookies
• No backend server — the app is a static site with API proxies for live price feeds
• For maximum privacy, clone this repo and run it locally

Supported Import Providers

Provider	Format	What's imported
ComputerShare	CSV (transaction history)	Stock lots with per-lot cost basis and dates
Gemini	XLSX (transaction history)	Crypto positions with FIFO cost basis
Fidelity	CSV (portfolio positions)	Brokerage holdings with cost basis
Transamerica	CSV (fund-holdings + source-balance)	401(k) accounts by source type
Any CSV	Custom column mapping	Heuristic detection + manual override

Features

Dashboard

• Net position summary with live prices
• Cash flow trajectory
• Asset breakdown by platform and type

Tax Engine

• Progressive federal brackets (2025–2026)
• All 50 states + DC
• Long-term capital gains with LTCG stacking method
• Net Investment Income Tax (NIIT) auto-calculation
• 4 filing statuses: Single, MFJ, MFS, HOH
• Flat-rate override mode for quick estimates

Purchase Planning

• Home purchase: down payment, closing costs, PMI analysis, property tax
• Vehicle purchase: down payment, dealer fees, financing
• Liquidation analysis: which assets to sell to fund the purchase
• Readiness projections: when will you have enough?

Mortgage Tools

• Full amortization schedule
• Points buy-down with opportunity cost break-even
• PMI calculation and removal timeline
• Multi-lender comparison (APR, total cost, break-even)
• Conforming vs. jumbo loan detection (FHFA limits by county)

Import & Data Management

• One-click import from supported brokerages
• Encrypted backup/restore (AES-256-GCM, password-protected)
• Plain JSON backup for transparency
• "Seed with example data" for exploration

External Price Feeds

GreenLight fetches live prices automatically — no API keys required for basic use:

Source	What it provides	Key required?
Gemini	Crypto prices (BTC, ETH, and ~18 others)	No
CoinGecko	Additional crypto (POL/MATIC)	No
Yahoo Finance	Stock prices (proxied)	No
Finnhub	Stock price fallback	No (optional, improves fallback reliability)
FRED	Live mortgage rates	No (optional; app works without it)

Prices refresh every 15 minutes and are cached in IndexedDB for 90 days.

Development

npm run dev          # Dev server with HMR (localhost:5173)
npm run build        # Production build → dist/
npm run preview      # Preview production build
npm run lint         # ESLint
npm test             # Vitest — run all tests once
npm run test:watch   # Vitest — watch mode
npm run build:limits # Regenerate FHFA conforming loan limit data

Using Your Own Financial Data (Local Dev)

Place your export files in data/user_[initials]/[provider]/:

data/
  user_jd/
    computershare/
      Transactions-2024.csv
    gemini/
      transaction_history.xlsx
    fidelity/
      Portfolio_Positions_Mar-01-2026.csv
    transamerica/
      fund-holdings.csv
      source-balance.csv

When running npm run dev, GreenLight will detect these files on startup and offer to import them.

Adding a New Provider Parser

1. Create src/lib/parsers/yourprovider.js — export a parseYourProviderCSV(text, filename) function
2. Add the provider to src/data/providers.js
3. Handle the new platform in src/pages/Import.jsx
4. Add inline fixture tests in src/lib/__tests__/parsers/yourprovider.test.js

See docs/ARCHITECTURE.md for the full parser contract.

Architecture

See docs/ARCHITECTURE.md for technical details including the state schema, data flow, and calculation layer design.

Contributing

See CONTRIBUTING.md for guidelines.

License

Apache License 2.0 with Commons Clause. Free for personal use; commercial resale is not permitted. See LICENSE for full terms.

Disclaimer

GreenLight provides tax estimates and financial projections for personal planning purposes only. The tax engine approximates your liability using published federal and state brackets and standard deductions — it does not account for all deductions, credits, AMT exposure, or other individual circumstances that a CPA would consider.

This tool is not a substitute for professional tax or legal advice. Always verify numbers with a qualified accountant or financial advisor before making significant financial decisions.