What are API Routes in Next.js?

API Routes in Next.js are a way to create server-side API endpoints right inside a Next.js project, without a separate backend application. They let you handle requests, work with data, and return JSON just like a regular REST API.

---

#Where they live

There are two options, depending on the router:

#Pages Router

Files in the folder:

/pages/api/*.ts

Each file is a separate API endpoint.

---

#App Router (Route Handlers)

Files of the form:

/app/api/.../route.ts

This is the modern version of API Routes, better integrated with the App Router.

---

#Where the code runs

• API Routes always run on the server
• the code never reaches the browser
• you can safely use:
  • secret keys
  • database access
  • server SDKs

---

#Why they are needed

API Routes are used to:

• hide API keys from the client
• proxy requests to external APIs
• work with a database
• handle forms
• do authorization
• combine several data sources
• implement simple backend logic

In effect, this is a mini-backend inside Next.js.

---

#How they are used with the frontend

From the client they are called like a regular API:

In this case:

• the logic stays on the server
• the client only gets the result

---

#Difference from client-side fetching

• client-side fetching - requests from the browser
• API Routes - server-side code, which can be called:
  • from the client
  • from Server Components
  • from other API Routes

---

#When API Routes are a good choice

• small or medium server logic
• no separate backend is needed
• a fullstack application in a single repository
• prototypes, startups, SaaS

---

#When not to use them

• complex business logic
• heavy load
• a microservices architecture
• the need for long-running processes

In such cases, a separate backend is more common.

---

#Short summary

• API Routes are server endpoints inside Next.js
• they run only on the server
• suited for working with the DB, APIs, and secrets
• let you do without a separate backend
• in the App Router they are implemented through Route Handlers