Next.js Playground — Learn the App Router with 26 Interactive Lessons

Next.js is the most widely adopted React framework for production web apps. It gives you file-based routing (folders become routes with no router config), shared and nested layouts, Server and Client Components that ship less JavaScript, built-in API route handlers for full-stack code in one project, and rendering choices (SSR, SSG, ISR) you pick per page for speed and SEO. You also get automatic code splitting, image and font optimization, prefetching, middleware on the edge, and a fast developer experience with TypeScript support. Because it is built on React, your component skills carry straight over. This playground teaches those benefits hands-on across 26 lessons, from your first page to dynamic routes, caching, metadata, and deployment.

Yes. This Next.js playground runs entirely in your browser. All 26 lessons transpile your JSX with Babel and render it through React inside a sandboxed iframe, so you can edit page.jsx, layout.jsx, globals.css, and a route handler and see a live result without installing Node.js, npm, or a dev server. It is built for learning and prototyping App Router patterns. When you want to build a real app, export the ZIP and run npm install plus npm run dev locally.

Some React helps but is not required. The early chapters cover JSX, expressions, components, props, lists, and conditional rendering, and the Client Components chapter teaches useState, events, controlled inputs, and useEffect. If you want a deeper React foundation first, work through the React Playground for hooks and component patterns, then return here to learn how Next.js adds routing, layouts, and route handlers around them.

There are 26 lessons across 10 chapters, beginner to pro: App Router Basics (pages, JSX, the default export as a route), Layouts (shared and nested layouts), Components & Props (components, props, lists and keys, conditional rendering), Client Components & State (use client, useState, events, controlled inputs, useEffect), Route Handlers (GET, dynamic JSON, fetching in a component), Styling (global CSS, class names, inline styles), Data & Rendering Patterns (loading states, error handling, deriving UI from data), Navigation (Link, in-page section nav), Patterns & Project (reusable components and a mini dashboard), and a Going to Production chapter (dynamic routes, Server vs Client Components, loading & streaming, data fetching & caching, the Metadata/SEO API, and middleware & deploying).

Yes. Every lesson executes for real in the browser. Edit any line of page.jsx and the live preview updates immediately, with the page mounted inside layout.jsx exactly as the App Router composes them. React hooks like useState and useEffect work, and route-handler lessons wire fetch("/api/hello") to your GET function so a page can call its own API. A console panel captures log, warning, and error output, and a runtime error strip surfaces problems near the preview.

No. The playground is a learning and prototyping environment, not the full framework. It does not run the Next.js compiler, the Server Components runtime, middleware, the image optimizer, or the production build pipeline. It focuses on the App Router files developers work with most — page, layout, CSS, and a route handler — so you can learn the model fast. Export the ZIP when you need real Next.js behavior.

Yes. The Route Handlers chapter includes app/api/hello/route.js and a panel that runs GET /api/hello inside the preview sandbox. You can edit the returned JSON, test Response.json output, and see how a page fetches that route with useEffect — a common App Router page-to-route workflow you can practice without a backend server.

Yes. Export ZIP creates a small Next.js project containing package.json, next.config.mjs, and the current app files. After downloading, unzip it, run npm install, then run npm run dev. The export turns a browser lesson or prototype into a normal local development workflow. Your progress and current files are also autosaved in your browser via localStorage and are never uploaded to a server.

The React Playground focuses on components, JSX, and hooks in a single-file editor. The Next.js Playground teaches how App Router files relate to each other — page.jsx, layout.jsx, globals.css, and route.js — plus routing, layouts, route handlers, and data patterns. Use the React Playground to master hooks and component patterns, then use this Next.js Playground to learn project structure and route-level behavior.