Nextjs Demo App

Next.js Demo App

The demo app in apps/demo-app shows the adapter running inside a Next.js App Router application.

Features

• Email/password registration and login through Better Auth.
• Better Auth API route under /api/auth.
• Protected dashboard route.
• Cosmos DB persistence through the local workspace package.

Important Files

File	Purpose
apps/demo-app/src/lib/auth.ts	Creates and caches the Better Auth server instance.
apps/demo-app/src/app/api/auth/[...all]/route.ts	Exposes Better Auth GET and POST handlers for Next.js.
apps/demo-app/src/lib/authClient.ts	Creates the browser-side Better Auth client.
apps/demo-app/src/app/login/page.tsx	Login page.
apps/demo-app/src/app/register/page.tsx	Registration page.
apps/demo-app/src/app/dashboard/page.tsx	Protected dashboard page.

Environment

Create apps/demo-app/.env.local:

NEXT_PUBLIC_AUTH_URL="http://localhost:3000"
NEXTAUTH_URL="http://localhost:3000"

COSMOS_ENDPOINT="https://<your-account>.documents.azure.com:443/"
COSMOS_KEY="<cosmos-key>"
COSMOS_DB_NAME="better-auth-demo"

The server config also accepts COSMOS_DB_ENDPOINT and COSMOS_DB_KEY.

Run Locally

From the repository root:

pnpm install
pnpm --filter demo-app dev

Then open:

http://localhost:3000

Auth Configuration

The demo uses:

authInstance = betterAuth({
  database: adapter,
  emailAndPassword: {
    enabled: true,
  },
  trustedOrigins: ['http://localhost:3000', 'http://localhost:5173'],
  baseURL: process.env.NEXTAUTH_URL || process.env.NEXT_PUBLIC_AUTH_URL || 'http://localhost:3000',
  basePath: '/api/auth',
});

The adapter is initialized with usePlural: true, so the demo database uses plural container names.