API Routes in Next.js — Your First Server-Side Endpoint

Up until now, we've been on the consuming side of APIs — making requests, reading responses, handling errors. Now we flip to the other side. You're going to build the API.

Next.js makes this remarkably straightforward. You don't need to set up a separate backend server. You don't need Express. You don't need to configure a reverse proxy. You just create a file in the right place, export some functions, and you have a working API endpoint.

How Next.js API Routes Work

In the Next.js App Router, API routes are called Route Handlers. They live in the app/api/ directory and are defined in files named route.ts.

The directory path becomes the URL path:

app/api/users/route.ts          →  /api/users
app/api/users/[id]/route.ts     →  /api/users/42
app/api/posts/route.ts