A practical comparison of React SPA and Next.js App Router - when to use each, trade-offs to consider, and how to migrate between them.
The Question I Get Asked All the Time
"What's the difference between React and Next.js?" and "Which one should I use?" - these come up constantly in team discussions and code reviews.
React is a Library, Next.js is a Framework
This is the fundamental distinction. React gives you components and state management. Next.js gives you a complete application architecture - routing, server-side rendering, image optimization, API routes, and more.
When to Choose React SPA
If you're building a client-heavy application like a dashboard where most interaction happens after initial load, a pure React SPA can be the right call. The cold start overhead doesn't matter when users stay for 30+ minutes.
When Next.js Makes Sense
For most web applications today, Next.js App Router is the better default. Server components reduce client-side JavaScript, the routing is more intuitive, and the performance optimizations are built in rather than bolted on.
The Migration Path
Good news: migrating from Create React App to Next.js can be gradual. You don't have to rewrite everything at once - start with the pages that would benefit most from SSR.