better-auth

SKILL.md

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: "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

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