Better Auth Skill for Claude

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.

When to Use

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

Quick Start

Installation

npm install better-auth
# or pnpm/yarn/bun add better-auth

Environment Setup

Create .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/):

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!,
    }
  }
});

Database Schema

npx @better-auth/cli generate  # Generate schema/migrations
npx @better-auth/cli migrate   # Apply migrations (Kysely only)

Mount API Handler

Next.js App Router:

// app/api/auth/[...all]/route.ts
import { auth } from "@/lib/auth";
import { toNextJsHandler } from "better-auth/next-js";

export const { POST, GET } = toNextJsHandler(auth);

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

Client Setup

Create auth-client.ts:

import { createAuthClient } from "better-auth/client";

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

Basic Usage

// Sign up
await authClient.signUp.email({
  email: "[email protected]",
  password: "secure123",
  name: "John Doe"
});

// Sign in
await authClient.signIn.email({
  email: "[email protected]",
  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

Feature Selection Matrix

| Feature | Plugin Required | Use Case | Reference |

|---------|----------------|----------|-----------|

| Email/Password | No (built-in) | Basic auth | email-password-auth.md |

| OAuth (GitHub, Google, etc.) | No (built-in) | Social login | oauth-providers.md |

| Email Verification | No (built-in) | Verify email addresses | email-password-auth.md |

| Password Reset | No (built-in) | Forgot password flow | email-password-auth.md |

| Two-Factor Auth (2FA/TOTP) | Yes (twoFactor) | Enhanced security | advanced-features.md |

| Passkeys/WebAuthn | Yes (passkey) | Passwordless auth | advanced-features.md |

| Magic Link | Yes (magicLink) | Email-based login | advanced-features.md |

| Username Auth | Yes (username) | Username login | email-password-auth.md |

| Organizations/Multi-tenant | Yes (organization) | Team/org features | advanced-features.md |

| Rate Limiting | No (built-in) | Prevent abuse | advanced-features.md |

| Session Management | No (built-in) | User sessions | advanced-features.md |

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:

• Server (better-auth): Handles auth logic, database ops, API routes
• Client (better-auth/client): Provides hooks/methods for frontend
• 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

Reference Documentation

Core Authentication

• Email/Password Authentication - Email/password setup, verification, password reset, username auth
• OAuth Providers - Social login setup, provider configuration, token management
• Database Integration - Database adapters, schema setup, migrations

Advanced Features

• Advanced Features - 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