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Getting Started with App Router

Getting Started with App Router

Section titled “Getting Started with App Router”

Introduction

Section titled “Introduction”

The App Router is Next.js’s modern routing system, introduced as stable in Next.js 13.4. It’s built on top of React Server Components, providing a powerful way to create routes using a file-system based convention. The App Router uses a special app/ directory where folders define routes and files define UI for each route segment.

Why this topic exists

Section titled “Why this topic exists”

Before you can build applications with the App Router, you need to understand its core concepts: how routes are defined, what special files like layout.tsx and page.tsx do, and how to structure your application for maximum maintainability.

Learning objectives

Section titled “Learning objectives”

By the end of this module, you will be able to:

  • Understand what the App Router is and how it differs from the Pages Router
  • Create routes using the app/ directory convention
  • Implement nested layouts that persist across pages
  • Create loading UIs and error boundaries
  • Set up custom 404 pages
  • Navigate between pages using the Link component and useRouter

Prerequisites

Section titled “Prerequisites”
  • Completed Phase 1: Next.js Fundamentals
  • Basic understanding of React components and hooks
  • Node.js 16.14+ installed

Learning roadmap

Section titled “Learning roadmap”
  1. What is the App Router?
  2. Layouts and Templates
  3. Page, Loading, Error, and Not Found Files
  4. Linking and Navigation

Topics covered

Section titled “Topics covered”
  • App Router vs Pages Router comparison
  • The app/ directory structure
  • File conventions: layout.tsx, page.tsx, loading.tsx, error.tsx, not-found.tsx
  • Nested layouts and layout composition
  • Loading UI with loading.tsx and Suspense
  • Error boundaries with error.tsx
  • Custom 404 pages with not-found.tsx
  • Client-side navigation with next/link and useRouter

Estimated learning time

Section titled “Estimated learning time”

8-10 hours to complete all topics and exercises.

Real-world applications

Section titled “Real-world applications”
  • Multi-page websites with shared navigation and footer
  • Dashboards with persistent sidebars
  • E-commerce sites with consistent layout across product pages
  • Blog platforms with section-specific layouts
  • SaaS applications with role-based layouts

Practice exercises

Section titled “Practice exercises”
  1. Set up an App Router project and create your first routes
  2. Build a nested layout hierarchy (root layout → section layout → page)
  3. Add loading spinners for slow-loading routes
  4. Implement error boundaries with fallback UI
  5. Build a navigation system with active route highlighting

Mini Project

Section titled “Mini Project”

Create a company website with:

  • Root layout containing header, navigation, and footer
  • A blog section with its own layout (sidebar + main content)
  • Loading states for each section
  • Custom error pages
  • A 404 page for unknown routes
  • Proper navigation using the Link component
Section titled “Related Topics”
  • Dynamic Routes (Module 2)
  • Route Groups (Module 2)
  • Data Fetching (Phase 3)
  • Server Components