Getting Started with Next.js 15

Next.js 15 is a big step forward for React. It improves the App Router, upgrades Server Components, and adds several performance gains. Because of this, it has become a popular choice for building production web applications.

Why Next.js 15?

The framework has matured a lot since its early days. Next.js 15 makes features that used to be experimental stable, and it adds new tools that make full-stack development easier.

• Stable App Router with improved caching semantics
• Turbopack as the default bundler for development
• Enhanced Server Actions with better error handling
• Partial Prerendering for optimal loading performance
• Improved TypeScript support and type inference

Setting Up Your Project

Getting started with Next.js 15 is straightforward. The create-next-app CLI has been updated with new templates and improved defaults.

npx create-next-app@latest my-app --typescript --tailwind --app
cd my-app
npm run dev

This sets up a project with TypeScript, Tailwind CSS, and the App Router, which is the recommended stack for new projects.

Understanding the App Router

The App Router uses a file-system based routing mechanism where folders define routes. Each folder can contain a page.tsx for the UI, layout.tsx for shared layouts, and loading.tsx for streaming states.

// app/blog/[slug]/page.tsx
export default async function BlogPost({
  params,
}: {
  params: { slug: string };
}) {
  const post = await getPost(params.slug);
  return <article>{post.content}</article>;
}

Server Components by Default

In Next.js 15, components are Server Components by default. This means they render on the server, reducing the JavaScript sent to the client. You only opt into client-side interactivity when you need it with the 'use client' directive.

This change leads to faster initial page loads, better SEO, and a clearer idea of where your code runs. With Partial Prerendering, you also get both static and dynamic rendering in the same app.