How to Structure a Full-Stack Next.js 15 Project in 2026

Next.js 15 shipped major changes: App Router is the default, Server Components are the norm, Server Actions replace most API routes, and Turbopack changes the build story. Most project structure guides are outdated. Here's what actually works in production. What Changed in Next.js 15 App Router Is the Default The pages/ directory still works but app/ is where new features land. Parallel routes, intercepting routes, route groups, and streaming — all App Router only. Start new projects with app/ . Server Components Eliminate Most API Routes In Next.js 14+, components are Server Components by default. They fetch data directly — no API route, no client-side fetch, no loading state boilerplate: // app/dashboard/page.tsx — this runs on the server async function DashboardPage () { const metrics = await db . query ( ' SELECT * FROM metrics WHERE date = $1 ' , [ today ]); return < MetricsGrid data = { metrics } /> ; } Server Actions Replace Form Handling Forms no longer need API routes or clien