What are API Routes?

API Routes are a way to create server-side API endpoints right inside Next.js, without a separate backend server.

In other words: Next.js can be both the frontend and the backend at the same time.

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#The basic idea

You describe a route, and Next.js turns it into an API:

• an HTTP request arrives (GET, POST, etc.)
• the code runs on the server
• JSON or another response is returned
• the browser or a server component gets the result

In this setup:

• the code never reaches the client
• you can work with the DB, tokens, secrets
• you don't need a separate Express / Nest / Fastify

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#Where API Routes exist

#Pages Router (the classic option)

• routes live in the /pages/api folder
• each file is a separate API endpoint

Example logic:

• /pages/api/posts → /api/posts
• /pages/api/user → /api/user

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#App Router (the modern option)

In the App Router, API Routes are called Route Handlers.

• they live next to pages
• they look like route.ts / route.js
• they explicitly support HTTP methods (GET, POST, PUT, DELETE)

In essence, it's the same API, but:

• closer to the application's file structure
• better integrated with Server Components and caching

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#What you can do in API Routes

You can:

• access a database
• work with authorization
• proxy requests to external APIs
• validate data
• hide API keys
• manage the cache

You cannot:

• use window or the DOM
• store state between requests (the server can be stateless)

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#Why they are needed

API Routes solve several tasks:

#1. Security

• API keys stay on the server
• the browser never sees them

#2. Simplifying the architecture

• no separate backend is needed
• less infrastructure
• simpler deployment

#3. A proxy between the client and external APIs

• client → API Route → external service
• data can be normalized
• responses can be cached

#4. Working with forms and actions

• submitting forms
• saving data
• server-side validation

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#API Routes and caching

API Routes:

• can use the cache
• can be dynamic
• can take part in ISR
• can run on the Edge or Node.js runtime

This makes them part of Next.js's overall data-handling system.

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#What API Routes are NOT

Important not to confuse:

• they are not a replacement for a full microservice backend
• not suited for long-running tasks
• do not store state between requests

They are ideal for:

• CRUD operations
• integrations
• logic "next to the UI"

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#In short

API Routes are:

• server functions inside Next.js
• accessible over HTTP
• secure
• tightly connected to rendering and caching

They let you keep data, logic, and UI in one project, without turning the application into a monolith.