Definitive Guide to Setting up Auth.js in Next.js 15

Step-by-step tutorial on configuring Auth.js (NextAuth) with the Prisma adapter in a Next.js 15 App Router project.

Last Updated • 7/2/2026

Introduction

Authentication is hard. Auth.js (formerly NextAuth.js) makes it easier. In this guide, we'll set up Auth.js with GitHub and Google providers in a modern Next.js 15 App Router project.

Prerequisites

Next.js 15 project
PostgreSQL database (Neon or local)
Prisma ORM

Step 1: Installation

First, install the core package and the Prisma adapter:

npm install next-auth @auth/prisma-adapter

Step 2: Configuration

Create the auth.ts config file at the root of your application.

Conclusion

You now have robust, edge-compatible authentication.

Guide FAQ

Can I use Auth.js at the edge?

Yes, but you need an edge-compatible database driver or you should split your auth config to avoid initializing the Prisma Client on the edge.