Getting Started

Visit https://paretojs.tech/guides/introduction to get started with Pareto.

What is Pareto?

Pareto is a lightweight React SSR framework that prioritizes streaming. Built on Vite for instant dev starts, it provides file-based routing, NDJSON streaming for client navigation, per-route head management via React components, and Immer-powered state with automatic SSR hydration.

npx create-pareto my-app
cd my-app && npm install && npm run dev

Performance

Pareto is built for throughput. In CI benchmarks against Next.js, React Router, and TanStack Start on identical hardware (Node 22, Ubuntu, 4 CPUs):

| Scenario | Pareto | Next.js | React Router | TanStack Start | |---|---:|---:|---:|---:| | Data Loading | 2,733/s | 293/s | 955/s | 1,386/s | | Streaming SSR | 247/s | 236/s | 247/s | 247/s | | API / JSON | 3,675/s | 2,212/s | 1,950/s | — | | Static SSR | 2,224/s | 3,328/s | 997/s | 2,009/s |

Under ramp-up load (1→1000 concurrent connections), Pareto sustains the highest QPS before hitting the p99 < 500ms threshold:

| Scenario | Pareto | Next.js | React Router | TanStack Start | |---|---:|---:|---:|---:| | Data Loading | 2,735/s | 331/s | 1,044/s | 1,458/s | | Streaming SSR | 2,022/s | 310/s | 807/s | 960/s | | API / JSON | 3,556/s | 1,419/s | 1,912/s | — |

Client JS sent to the browser: 62 KB gzipped (vs Next.js 233 KB, React Router 100 KB, TanStack Start 101 KB).

In practice: a data-loading page serving 2,000 req/s at peak needs 1 Pareto server vs 6 Next.js instances. For streaming SSR, it's 1 vs 7.

Benchmark details: PR #12

Features

• Streaming SSR — renderToPipeableStream with defer() for progressive data delivery through Suspense
• Vite-powered — Instant dev starts, React Fast Refresh, native ESM in development
• File-based routing — page.tsx · layout.tsx · loader.ts · head.tsx · document.tsx · not-found.tsx
• Client navigation — SPA-feel <Link> with prefetching, backed by NDJSON streaming
• Head management — Per-route head.tsx React components with nested merge and deduplication
• State management — Immer-powered defineStore() and defineContextStore() with automatic SSR hydration
• TypeScript-first — Full type safety across loaders, pages, and configuration
• Security headers — Built-in OWASP baseline middleware

Documentation

Visit paretojs.tech to view the full documentation.

Packages

• @paretojs/core — Core framework
• create-pareto — Project scaffolding CLI

Community

• GitHub Issues — Bug reports and feature requests
• GitHub Discussions — Questions and ideas

Contributing

Contributions are welcome. Please open an issue first to discuss what you would like to change.

License

MIT