better-auth

name	better-auth
description	Provides Better Auth integration patterns for NestJS backend and Next.js frontend with Drizzle ORM and PostgreSQL. Use when setting up Better Auth with NestJS backend, integrating Next.js App Router frontend, configuring Drizzle ORM schema, implementing social login (GitHub, Google), adding plugins (2FA, Organization, SSO, Magic Link, Passkey), implementing email/password authentication with session management, or creating protected routes and middleware.
allowed-tools	Read, Write, Edit, Glob, Grep, Bash

Better Auth Integration Guide

Overview

Better Auth is a type-safe authentication framework for TypeScript supporting multiple providers, 2FA, SSO, organizations, and passkeys. This skill covers integration patterns for NestJS backend with Drizzle ORM + PostgreSQL and Next.js App Router frontend.

When to Use

• Setting up Better Auth with NestJS backend
• Integrating Next.js App Router frontend
• Configuring Drizzle ORM schema with PostgreSQL
• Implementing social login (GitHub, Google, Facebook, Microsoft)
• Adding MFA/2FA with TOTP, passkey passwordless auth, or magic links
• Managing trusted devices and backup codes for account recovery
• Building multi-tenant apps with organizations or SSO
• Creating protected routes with session management

Quick Start

Installation

# Backend (NestJS)
pnpm install better-auth @auth/drizzle-adapter drizzle-orm pg
pnpm install -D drizzle-kit

# Frontend (Next.js)
pnpm install better-auth

4-Phase Setup

1. Database: Install Drizzle, configure schema, run migrations
2. Backend: Create Better Auth instance with NestJS module
3. Frontend: Configure auth client, create pages, add middleware
4. Plugins: Add 2FA, passkey, organizations as needed

See references/nestjs-setup.md for complete backend setup, references/plugins.md for plugin configuration.

Instructions

Phase 1: Database Setup

1. Install dependencies

   pnpm install drizzle-orm pg @auth/drizzle-adapter better-auth
   pnpm install -D drizzle-kit
   

2. Create Drizzle config (drizzle.config.ts)

   import { defineConfig } from "drizzle-kit";
   export default defineConfig({
     schema: "./src/auth/schema.ts",
     out: "./drizzle",
     dialect: "postgresql",
     dbCredentials: { url: process.env.DATABASE_URL! },
   });
   

3. Generate and run migrations

   pnpx drizzle-kit generate
   pnpx drizzle-kit migrate
   

   Checkpoint: Verify tables created: psql $DATABASE_URL -c "\dt" should show user, account, session, verification_token tables.

Phase 2: Backend Setup (NestJS)

1. Create database module - Set up Drizzle connection service

2. Configure Better Auth instance

   // src/auth/auth.instance.ts
   import { betterAuth } from "better-auth";
   import { drizzleAdapter } from "@auth/drizzle-adapter";
   import * as schema from "./schema";
   
   export const auth = betterAuth({
     database: drizzleAdapter(schema, { provider: "postgresql" }),
     emailAndPassword: { enabled: true },
     socialProviders: {
       github: {
         clientId: process.env.AUTH_GITHUB_CLIENT_ID!,
         clientSecret: process.env.AUTH_GITHUB_CLIENT_SECRET!,
       },
     },
   });
   

3. Create auth controller

   @Controller("auth")
   export class AuthController {
     @All("*")
     async handleAuth(@Req() req: Request, @Res() res: Response) {
       return auth.handler(req);
     }
   }
   

   Checkpoint: Test endpoint GET /auth/get-session returns { session: null } when unauthenticated (no error).

Phase 3: Frontend Setup (Next.js)

1. Configure auth client (lib/auth.ts)

   import { createAuthClient } from "better-auth/client";
   export const authClient = createAuthClient({
     baseURL: process.env.NEXT_PUBLIC_APP_URL!,
   });
   

2. Add middleware (middleware.ts)

   import { auth } from "@/lib/auth";
   export default auth((req) => {
     if (!req.auth && req.nextUrl.pathname.startsWith("/dashboard")) {
       return Response.redirect(new URL("/sign-in", req.nextUrl.origin));
     }
   });
   export const config = { matcher: ["/dashboard/:path*"] };
   

3. Create sign-in page with form or social buttons

   Checkpoint: Navigating to /dashboard when logged out should redirect to /sign-in.

Phase 4: Advanced Features

Add plugins from references/plugins.md:

• 2FA: twoFactor({ issuer: 'AppName', otpOptions: { sendOTP } })

• Passkey: passkey({ rpID: 'domain.com', rpName: 'App' })

• Organizations: organization({ avatar: { enabled: true } })

• Magic Link: magicLink({ sendMagicLink })

• SSO: sso({ saml: { enabled: true } })

  Checkpoint: After adding plugins, re-run migrations and verify new tables exist.

Examples

Example 1: Server Component with Session

Input: Display user data in a Next.js Server Component.

// app/dashboard/page.tsx
import { auth } from "@/lib/auth";
import { redirect } from "next/navigation";

export default async function DashboardPage() {
  const session = await auth();

  if (!session) {
    redirect("/sign-in");
  }

  return (
    <div>
      <h1>Welcome, {session.user.name}</h1>
      <p>Email: {session.user.email}</p>
    </div>
  );
}

Output: Renders user info for authenticated users; redirects unauthenticated to sign-in.

Example 2: 2FA TOTP Verification with Trusted Device

Input: User has 2FA enabled and wants to sign in, marking device as trusted.

// Server: Configure 2FA with OTP sending
export const auth = betterAuth({
  plugins: [
    twoFactor({
      issuer: "MyApp",
      otpOptions: {
        async sendOTP({ user, otp }, ctx) {
          await sendEmail({
            to: user.email,
            subject: "Your verification code",
            body: `Code: ${otp}`,
          });
        },
      },
    }),
  ],
});

// Client: Verify TOTP and trust device
const verify2FA = async (code: string) => {
  const { data } = await authClient.twoFactor.verifyTotp({
    code,
    trustDevice: true, // Device trusted for 30 days
  });

  if (data) {
    router.push("/dashboard");
  }
};

Output: User authenticated; device trusted for 30 days without 2FA prompt.

Example 3: Passkey Registration and Login

Input: Enable passkey (WebAuthn) authentication for passwordless login.

// Server
import { passkey } from "@better-auth/passkey";
export const auth = betterAuth({
  plugins: [
    passkey({
      rpID: "example.com",
      rpName: "My App",
    }),
  ],
});

// Client: Register passkey
const registerPasskey = async () => {
  const { data } = await authClient.passkey.register({
    name: "My Device",
  });
};

// Client: Sign in with autofill
const signInWithPasskey = async () => {
  await authClient.signIn.passkey({
    autoFill: true, // Browser suggests passkey
  });
};

Output: Users can register and authenticate with biometrics, PIN, or security keys.

For more examples (backup codes, organizations, magic link, conditional UI), see references/plugins.md and references/passkey.md.

Best Practices

1. Environment Variables: Store all secrets in .env, add to .gitignore
2. Secret Generation: Use openssl rand -base64 32 for BETTER_AUTH_SECRET
3. HTTPS Required: OAuth callbacks need HTTPS (use ngrok for local testing)
4. Session Expiration: Configure based on security requirements (7 days default)
5. Database Indexing: Add indexes on email, userId for performance
6. Error Handling: Return generic errors without exposing sensitive details
7. Rate Limiting: Add to auth endpoints to prevent brute force attacks
8. Type Safety: Use pnpx better-auth typegen for full TypeScript coverage

Constraints and Warnings

Security Notes

• Never commit secrets: Add .env to .gitignore; never commit OAuth secrets or DB credentials
• Validate redirect URLs: Always validate OAuth redirect URLs to prevent open redirects
• Hash passwords: Better Auth handles password hashing automatically; never implement custom hashing
• Session storage: For production, use Redis or another scalable session store
• HTTPS Only: Always use HTTPS for authentication in production
• Email Verification: Always implement email verification for password-based auth

Known Limitations

• Better Auth requires Node.js 18+ for Next.js App Router support
• Some OAuth providers require specific redirect URL formats
• Passkeys require HTTPS and compatible browsers
• Organization features require additional database tables

Resources

Documentation

• Better Auth - Official documentation
• NestJS - Backend framework
• Next.js - Frontend framework

Reference Implementations

• references/nextjs-setup.md - Complete Next.js frontend setup
• references/plugins.md - Plugin configuration (2FA, passkey, organizations, SSO, magic link)
• references/mfa-2fa.md - Detailed MFA/2FA guide
• references/passkey.md - Detailed passkey implementation
• references/social-providers.md - Social provider configuration