Why is Next.js considered a fullstack framework?

Next.js is considered a fullstack framework because within one project it combines frontend + backend + server-side rendering, without needing to run a separate server.

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#What makes Next.js fullstack

#1. Server code next to the UI

In Next.js you can write code that:

• runs only on the server
• has access to the DB, secrets, the file system
• never reaches the browser

Example:

• Server Components
• Server Actions

This is already backend logic, not just frontend.

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#2. API Routes (built-in backend)

Next.js lets you create API endpoints right in the project:

• REST / RPC
• form handling
• auth
• webhooks
• integrations with third-party services

Without Express / Nest / Fastify.

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#3. Working with the database directly

On the server side of Next.js you can:

• connect to a DB (PostgreSQL, MySQL, etc.)
• run ORM/SQL queries
• validate data

UI -> Server Action -> DB Without a separate backend application.

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#4. Managing data on the server

Next.js takes care of:

• SSR / SSG / ISR
• data caching
• revalidate
• streaming

That is, the server manages the data, not the browser.

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#5. Authorization and security

In Next.js you can:

• read cookies / headers
• check sessions
• hide business logic
• work with tokens

These are typical backend tasks.

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#6. A single project architecture

In one repository:

• UI (React)
• routes
• server logic
• API
• rendering
• optimization

Less infrastructure Less syncing Faster development

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#What is important to understand (a common trap)

Next.js is not a replacement for a complex backend.

• complex domain services
• heavy background jobs
• complex queues
• microservices

For that, it's better to have:

• Next.js - frontend + BFF
• a separate backend (Nest.js, Spring, etc.)

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#Short answer for an interview

Next.js is considered a fullstack framework because it lets you implement the UI, server-side rendering, an API, and database work in a single project, without a separate backend application.