Better Auth

TypeScript-first authentication for Next.js, Express, and React. Better Auth handles sessions, credentials, OAuth, and more.

Better Auth is a framework-agnostic TypeScript authentication library. StackKit sets it up with the right configuration for your framework so you can start authenticating users immediately.

Compatible frameworks

Better Auth works across all three StackKit frameworks:

Framework	Notes
Next.js	API routes, server-side session access, React hooks
Express	Mounted as a middleware with dedicated auth routes
React	Client-side session management and sign-in/sign-up flows

When using Better Auth with Express, a database is required. Better Auth needs somewhere to persist sessions and user records.

Installation

In a new project

npx stackkit@latest create my-app --auth better-auth

pnpm dlx stackkit@latest create my-app --auth better-auth

yarn dlx stackkit@latest create my-app --auth better-auth

bun x stackkit@latest create my-app --auth better-auth

In an existing project

npx stackkit@latest add
# Navigate to: Authentication → Better Auth

What gets generated

StackKit writes all the files Better Auth needs — you don't have to touch any configuration manually.

Next.js:

lib/auth.ts — Core auth configuration (plugins, social providers, etc.)
lib/auth-client.ts — Client-side hooks (useSession, signIn, signOut)
app/api/auth/[...all]/route.ts — API handler that mounts Better Auth

Express:

src/lib/auth.ts — Auth instance with database adapter
src/routes/auth.routes.ts — Express router for auth endpoints

React:

src/lib/auth-client.ts — Client configured for your backend URL

Setup

Copy your environment file

cp .env.example .env

Set your environment variables

Open .env and fill in:

BETTER_AUTH_SECRET="paste-your-generated-secret-here"
BETTER_AUTH_URL="http://localhost:3000"

For Express projects, use http://localhost:5000.

BETTER_AUTH_URL is the base URL of your application. In production, this should be your actual domain.

Run the database migration (if applicable)

If your project includes Prisma, Better Auth adds user and session tables to your schema. Apply them with:

npx prisma migrate dev --name better-auth-init

Start the development server

npm run dev

Environment variables

Variable	Required	Description
`BETTER_AUTH_SECRET`	Yes	Secret key for signing session tokens. Must be at least 32 characters.
`BETTER_AUTH_URL`	Yes	Base URL of your app (e.g., `http://localhost:3000` for Next.js/React, `http://localhost:5000` for Express).

The generated lib/auth.ts (or src/lib/auth.ts for Express) is where you configure Better Auth. You can add social providers, enable 2FA, set session duration, and more — all by editing this single file.

For example, to add Google OAuth:

import { betterAuth } from "better-auth";

export const auth = betterAuth({
  // ... existing config
  socialProviders: {
    google: {
      clientId: process.env.GOOGLE_CLIENT_ID!,
      clientSecret: process.env.GOOGLE_CLIENT_SECRET!,
    },
  },
});

For the full list of options, see the Better Auth documentation.

Next steps

Troubleshooting — Common auth-related issues