Next.js 15 App Router: Best Practices for Exceptional Performance
The App Router in Next.js 15 changes how you think about pages: Server Components by default, with a clear split between server and client logic.
extra JavaScript shipped to the browser from a non-interactive Server Component
single function (generateMetadata) covers all dynamic SEO needs
best balance between a fully static and fully dynamic page
The most important App Router rule: every component is a Server Component by default unless you add "use client" — meaning more logic runs on the server and less JavaScript ships to the browser.
Use generateMetadata Instead of Manual Head Tags
The async generateMetadata function lets you build dynamic title, description, and Open Graph data based on the page's actual data (like locale or slug) — cleaner and more powerful for SEO than manually placed head tags.
Caching and Revalidation
export const revalidate sets how often a page rebuilds in the background (ISR), an ideal middle ground between a fully static page and a fully dynamic per-request page — very useful for periodically changing content like a blog.
Questions & Answers
01When do I need "use client"?
Only when a component needs browser interactivity: state, effects, or event handlers like onClick.
02Does App Router fully replace Pages Router?
For new projects, yes — App Router is always recommended. Pages Router is still supported but doesn't get new features with the same priority.
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