IndexSwapy

A small web tool for traders that converts price levels between QQQ, NDX and NQ (Nasdaq) and between SPY and ES (S&P 500) using current ratios.

Features

• Conversions: QQQ to/from NDX, QQQ to/from NQ, SPY to/from ES
• Paste up to 50 values at once, separated by commas, spaces, dashes or new lines; results shown in a table
• Current NDX/QQQ, NQ/QQQ and ES/SPY ratios shown in the header, fetched from the companion indexswapy-backend API and cached for 60 seconds
• Light and dark theme

Tech stack

• React 19, TypeScript, Vite
• Tailwind CSS 4, shadcn/ui (Radix UI), lucide-react
• Netlify (static hosting with security headers)

Getting started

Prerequisites: Node.js 22+ (tests use --experimental-strip-types).

npm install
npm run dev

When running on localhost, the UI requests ratios from http://127.0.0.1:8888/api/ratios, so start the backend API on port 8888 first. Elsewhere it uses the deployed backend.

Other scripts:

npm test          # converter and input parsing tests
npm run lint
npm run typecheck
npm run build     # output in dist/

Deploy on Netlify with build command npm run build and publish directory dist (already set in netlify.toml).

Project structure

src/App.tsx                 Layout, ratio badges, theme toggle
src/components/             Converter panel, theme provider/toggle, shadcn/ui components
src/lib/converter.ts        Ratio fetching, caching and conversion math
src/lib/pairs.ts            Supported conversion pairs
src/lib/parse-input.ts      Multi-value input parsing
test/                       Node test script
netlify.toml                Build settings, CSP and security headers

Status

Active. Version 2.0.0, last updated October 2026.

License

MIT. See LICENSE. Contribution guidelines are in CONTRIBUTING.md.