better-auth - SKILL.md Agent Skill

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.

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: "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

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

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

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