Better Auth

---
name: better-auth
description: Implement authentication and authorization with Better Auth - a framework-agnostic TypeScript authentication framework. Features include email/password authentication with verification, OAuth providers (Google, GitHub, Discord, etc.), two-factor authentication (TOTP, SMS), passkeys/WebAuthn support, session management, role-based access control (RBAC), rate limiting, and database adapters. Use when adding authentication to applications, implementing OAuth flows, setting up 2FA/MFA, managing user sessions, configuring authorization rules, or building secure authentication systems for web applications.
license: MIT
version: 2.0.0
---

# Better Auth Skill

Better Auth is comprehensive, framework-agnostic authentication/authorization framework for TypeScript with built-in email/password, social OAuth, and powerful plugin ecosystem for advanced features.

<triggers>
<trigger>Implementing auth in TypeScript/JavaScript applications</trigger>
<trigger>Adding email/password or social OAuth authentication</trigger>
<trigger>Setting up 2FA, passkeys, magic links, advanced auth features</trigger>
<trigger>Building multi-tenant apps with organization support</trigger>
<trigger>Managing sessions and user lifecycle</trigger>
<trigger>Working with any framework (Next.js, Nuxt, SvelteKit, Remix, Astro, Hono, Express, etc.)</trigger>
</triggers>

## Quick Start

### Installation

<example type="usage">
<code language="bash">
npm install better-auth
# or pnpm/yarn/bun add better-auth
</code>
</example>

### Environment Setup

Create `.env`:
```env
BETTER_AUTH_SECRET=<generated-secret-32-chars-min>
BETTER_AUTH_URL=http://localhost:3000
```

### Basic Server Setup

Create `auth.ts` (root, lib/, utils/, or under src/app/server/):

<example type="usage">
<code language="typescript">
import { betterAuth } from "better-auth";

export const auth = betterAuth({
  database: {
    // See references/database-integration.md
  },
  emailAndPassword: {
    enabled: true,
    autoSignIn: true
  },
  socialProviders: {
    github: {
      clientId: process.env.GITHUB_CLIENT_ID!,
      clientSecret: process.env.GITHUB_CLIENT_SECRET!,
    }
  }
});
</code>
</example>

### Database Schema

<example type="usage">
<code language="bash">
npx @better-auth/cli generate  # Generate schema/migrations
npx @better-auth/cli migrate   # Apply migrations (Kysely only)
</code>
</example>

### Mount API Handler

**Next.js App Router:**

<example type="usage">
<code language="typescript">
// app/api/auth/[...all]/route.ts
import { auth } from "@/lib/auth";
import { toNextJsHandler } from "better-auth/next-js";

export const { POST, GET } = toNextJsHandler(auth);
</code>
</example>

**Other frameworks:** See references/email-password-auth.md#framework-setup

### Client Setup

Create `auth-client.ts`:

<example type="usage">
<code language="typescript">
import { createAuthClient } from "better-auth/client";

export const authClient = createAuthClient({
  baseURL: process.env.NEXT_PUBLIC_BETTER_AUTH_URL || "http://localhost:3000"
});
</code>
</example>

### Basic Usage

<example type="usage">
<code language="typescript">
// Sign up
await authClient.signUp.email({
  email: "user@example.com",
  password: "secure123",
  name: "John Doe"
});

// Sign in
await authClient.signIn.email({
  email: "user@example.com",
  password: "secure123"
});

// OAuth
await authClient.signIn.social({ provider: "github" });

// Session
const { data: session } = authClient.useSession(); // React/Vue/Svelte
const { data: session } = await authClient.getSession(); // Vanilla JS
</code>
</example>

## Feature Selection Matrix

| Feature | Plugin Required | Use Case | Reference |
|---------|----------------|----------|-----------|
| Email/Password | No (built-in) | Basic auth | [email-password-auth.md](./references/email-password-auth.md) |
| OAuth (GitHub, Google, etc.) | No (built-in) | Social login | [oauth-providers.md](./references/oauth-providers.md) |
| Email Verification | No (built-in) | Verify email addresses | [email-password-auth.md](./references/email-password-auth.md#email-verification) |
| Password Reset | No (built-in) | Forgot password flow | [email-password-auth.md](./references/email-password-auth.md#password-reset) |
| Two-Factor Auth (2FA/TOTP) | Yes (`twoFactor`) | Enhanced security | [advanced-features.md](./references/advanced-features.md#two-factor-authentication) |
| Passkeys/WebAuthn | Yes (`passkey`) | Passwordless auth | [advanced-features.md](./references/advanced-features.md#passkeys-webauthn) |
| Magic Link | Yes (`magicLink`) | Email-based login | [advanced-features.md](./references/advanced-features.md#magic-link) |
| Username Auth | Yes (`username`) | Username login | [email-password-auth.md](./references/email-password-auth.md#username-authentication) |
| Organizations/Multi-tenant | Yes (`organization`) | Team/org features | [advanced-features.md](./references/advanced-features.md#organizations) |
| Rate Limiting | No (built-in) | Prevent abuse | [advanced-features.md](./references/advanced-features.md#rate-limiting) |
| Session Management | No (built-in) | User sessions | [advanced-features.md](./references/advanced-features.md#session-management) |

## Auth Method Selection Guide

**Choose Email/Password when:**
- Building standard web app with traditional auth
- Need full control over user credentials
- Targeting users who prefer email-based accounts

**Choose OAuth when:**
- Want quick signup with minimal friction
- Users already have social accounts
- Need access to social profile data

**Choose Passkeys when:**
- Want passwordless experience
- Targeting modern browsers/devices
- Security is top priority

**Choose Magic Link when:**
- Want passwordless without WebAuthn complexity
- Targeting email-first users
- Need temporary access links

**Combine Multiple Methods when:**
- Want flexibility for different user preferences
- Building enterprise apps with various auth requirements
- Need progressive enhancement (start simple, add more options)

## Core Architecture

Better Auth uses client-server architecture:
1. **Server** (`better-auth`): Handles auth logic, database ops, API routes
2. **Client** (`better-auth/client`): Provides hooks/methods for frontend
3. **Plugins**: Extend both server/client functionality

## Implementation Checklist

- [ ] Install `better-auth` package
- [ ] Set environment variables (SECRET, URL)
- [ ] Create auth server instance with database config
- [ ] Run schema migration (`npx @better-auth/cli generate`)
- [ ] Mount API handler in framework
- [ ] Create client instance
- [ ] Implement sign-up/sign-in UI
- [ ] Add session management to components
- [ ] Set up protected routes/middleware
- [ ] Add plugins as needed (regenerate schema after)
- [ ] Test complete auth flow
- [ ] Configure email sending (verification/reset)
- [ ] Enable rate limiting for production
- [ ] Set up error handling

<constraints>
<constraint severity="critical">BETTER_AUTH_SECRET must be at least 32 characters and kept secure</constraint>
<constraint severity="critical">Never expose BETTER_AUTH_SECRET in client-side code</constraint>
<constraint severity="high">Always enable rate limiting in production to prevent brute force attacks</constraint>
<constraint severity="high">Regenerate database schema after adding/removing plugins</constraint>
<constraint severity="medium">Use HTTPS in production for all auth endpoints</constraint>
<constraint severity="medium">Implement email verification for email/password auth in production</constraint>
</constraints>

## Reference Documentation

### Core Authentication
- [Email/Password Authentication](./references/email-password-auth.md) - Email/password setup, verification, password reset, username auth
- [OAuth Providers](./references/oauth-providers.md) - Social login setup, provider configuration, token management
- [Database Integration](./references/database-integration.md) - Database adapters, schema setup, migrations

### Advanced Features
- [Advanced Features](./references/advanced-features.md) - 2FA/MFA, passkeys, magic links, organizations, rate limiting, session management

## Scripts

- `scripts/better_auth_init.py` - Initialize Better Auth configuration with interactive setup

## Resources

- Docs: https://www.better-auth.com/docs
- GitHub: https://github.com/better-auth/better-auth
- Plugins: https://www.better-auth.com/docs/plugins
- Examples: https://www.better-auth.com/docs/examples