Better Auth Flutter Client

A Flutter client package for Better Auth, enabling seamless authentication with Next.js backends. This package provides a type-safe, reactive authentication client that mirrors the Better Auth React client experience.

Features

• Email/Password Authentication: Sign in and sign up with email and password
• Session Management: Get, list, and revoke sessions
• OAuth Integration: Support for OAuth providers (Google, GitHub, etc.)
• Account Management: Update profile, change password, delete account
• Reactive State: ValueNotifier-based session state for UI updates
• Secure Storage: Automatic token storage using flutter_secure_storage
• Error Handling: Comprehensive error handling with typed error responses
• Input Validation: Built-in validators for common input fields

Getting Started

Prerequisites

• Flutter 3.10.0 or higher
• Dart 3.0.0 or higher
• A Next.js backend running Better Auth

Installation

Add this to your pubspec.yaml:

dependencies:
  better_auth_client: ^1.0.0

Then run:

flutter pub get

Server-Side Configuration

Ensure your Better Auth backend is configured for mobile authentication:

import { betterAuth } from "better-auth";
import { bearer } from "better-auth/plugins";

export const auth = betterAuth({
    plugins: [
        bearer()
    ],
    trustedOrigins: [
        "http://localhost:3000",
        "myapp://auth-callback",
    ],
    cors: {
        origin: [
            "http://localhost:3000",
            "myapp://auth-callback",
        ],
        credentials: true,
    },
});

Usage

Basic Setup

import 'package:better_auth_client/better_auth_client.dart';

final authClient = BetterAuthClient(
  baseUrl: String.fromEnvironment('BETTER_AUTH_URL', defaultValue: 'http://localhost:3000'),
);

Sign In

final response = await authClient.signIn.email(
  email: '[e-mail]',
  password: 'password123',
);

if (response.isSuccess) {
  print('Signed in as: ${response.data!.user.email}');
} else {
  print('Error: ${response.error!.message}');
}

Reactive Session Management

// Listen to session changes
ValueListenableBuilder<Session?>(
  valueListenable: authClient.sessionNotifier,
  builder: (context, session, child) {
    if (session == null) {
      return LoginPage();
    }
    return HomePage(session: session);
  },
);

// Get current session
final session = authClient.currentSession;

Sign Out

await authClient.signOut();

Session Management

// Get current session
final response = await authClient.session.get();

// List all sessions
final sessions = await authClient.session.list();

// Revoke other sessions
await authClient.session.revokeOthers();

OAuth Sign-In

final response = await authClient.oauth.signIn(
  provider: 'google',
  callbackUrlScheme: 'myapp',
);

if (response.isSuccess) {
  // OAuth sign-in successful
}

API Reference

BetterAuthClient

The main client class for authentication operations.

Properties

Property	Type	Description
baseUrl	String	The base URL of your Better Auth server
currentSession	Session?	The current session (synchronous access)
sessionNotifier	ValueNotifier<Session?>	ValueNotifier for reactive session updates
signIn	SignInModule	Module for sign-in operations
signUp	SignUpModule	Module for sign-up operations
session	SessionModule	Module for session management
oauth	OAuthModule	Module for OAuth operations
account	AccountModule	Module for account operations

Methods

Method	Returns	Description
getSession()	Future<AuthResponse<Session>>	Fetches the current session from the server
signOut()	Future<AuthResponse<void>>	Signs out the current user
dispose()	void	Disposes of client resources

SignInModule

Methods

Method	Parameters	Returns
email()	email: String, password: String	Future<AuthResponse<Session>>
otp()	email: String, otp: String	Future<AuthResponse<Session>>
anonymous()	-	Future<AuthResponse<Session>>

SignUpModule

Methods

Method	Parameters	Returns
email()	email: String, password: String, name: String?	Future<AuthResponse<User>>

SessionModule

Methods

Method	Parameters	Returns
get()	-	Future<AuthResponse<Session>>
list()	-	Future<AuthResponse<List<Session>>>
revoke()	sessionId: String	Future<AuthResponse<void>>
revokeOthers()	-	Future<AuthResponse<void>>

OAuthModule

Methods

Method	Parameters	Returns
signIn()	provider: String, callbackUrlScheme: String	Future<AuthResponse<Session>>

AccountModule

Methods

Method	Parameters	Returns
update()	name: String?, image: String?	Future<AuthResponse<User>>
changePassword()	newPassword: String, oldPassword: String?	Future<AuthResponse<void>>
delete()	-	Future<AuthResponse<void>>

Error Handling

All methods return an AuthResponse<T> that contains either the data or an AuthError:

final response = await authClient.signIn.email(email: email, password: password);

if (response.isSuccess) {
  // Handle success
  final session = response.data!;
} else {
  // Handle error
  final error = response.error!;
  print('Error code: ${error.code}');
  print('Error message: ${error.message}');
}

Common Error Codes

Code	Description
INVALID_CREDENTIALS	Email or password is incorrect
USER_NOT_FOUND	No account with this email
EMAIL_ALREADY_EXISTS	Account already exists
SESSION_EXPIRED	Session has expired
UNAUTHORIZED	Not authorized to perform action
VALIDATION_ERROR	Validation failed

Custom Storage

You can provide a custom storage implementation:

final authClient = BetterAuthClient(
  baseUrl: baseUrl,
  storage: MyCustomStorage(),
);

Example App

See the example directory for a complete example app demonstrating all features.

Contributing

Contributions are welcome! Please read our Code of Conduct and Contributing Guide before submitting PRs.

License

This package is licensed under the MIT License. See the LICENSE file for details.

Dependencies

Package	Description
dio	HTTP client for API requests
flutter_secure_storage	Secure storage for tokens
flutter_web_auth_2	OAuth authentication flow

Libraries

better_auth_flutter_client