NestJS Better Auth Integration

A comprehensive NestJS integration library for Better Auth, providing seamless authentication and authorization for your NestJS applications.

Installation

Install the library in your NestJS project:

# Using npm
npm install @thallesp/nestjs-better-auth

# Using yarn
yarn add @thallesp/nestjs-better-auth

# Using pnpm
pnpm add @thallesp/nestjs-better-auth

# Using bun
bun add @thallesp/nestjs-better-auth

Prerequisites

[!IMPORTANT]
Requires better-auth >= 1.3.8. Older versions are deprecated and unsupported.

Before you start, make sure you have:

• A working NestJS application
• Better Auth (>= 1.3.8) installed and configured (installation guide)

Basic Setup

1. Disable Body Parser

Disable NestJS's built-in body parser to allow Better Auth to handle the raw request body:

import { NestFactory } from "@nestjs/core";
import { AppModule } from "./app.module";

async function bootstrap() {
  const app = await NestFactory.create(AppModule, {
    // Don't worry, the library will automatically re-add the default body parsers.
    bodyParser: false,
  });
  await app.listen(process.env.PORT ?? 3333);
}
bootstrap();

[!WARNING]
Currently the library has beta support for Fastify, if you experience any issues with it, please open an issue.

2. Import AuthModule

Import the AuthModule in your root module:

import { Module } from "@nestjs/common";
import { AuthModule } from "@thallesp/nestjs-better-auth";
import { auth } from "./auth";

@Module({
  imports: [AuthModule.forRoot({ auth })],
})
export class AppModule {}

Route Protection

Global by default: An AuthGuard is registered globally by this module. All routes are protected unless you explicitly allow access with @AllowAnonymous() or mark them as optional with @OptionalAuth().

GraphQL is supported and works the same way as REST: the global guard applies to resolvers too, and you can use @AllowAnonymous()/@OptionalAuth() on queries and mutations.

WebSocket is also supported and works in the same way as REST and GraphQL: you can use @AllowAnonymous()/@OptionalAuth() on any connections, but you must set the AuthGuard for all of them, either at the Gateway or Message level, like so:

import { SubscribeMessage, WebSocketGateway } from "@nestjs/websockets";
import { UseGuards } from "@nestjs/common";
import { AuthGuard } from '@thallesp/nestjs-better-auth';

@WebSocketGateway({
	path: "/ws",
	namespace: "test",
	cors: {
		origin: "*",
	},
})
@UseGuards(AuthGuard)
export class TestGateway { /* ... */ }

Check the test gateway for a full example.

Decorators

Better Auth provides several decorators to enhance your authentication setup:

Session Decorator

Access the user session in your controllers:

import { Controller, Get } from "@nestjs/common";
import { Session, UserSession } from "@thallesp/nestjs-better-auth";

@Controller("users")
export class UserController {
  @Get("me")
  async getProfile(@Session() session: UserSession) {
    return session;
  }
}

AllowAnonymous, OptionalAuth, and Roles Decorators

Control authentication/authorization requirements for specific routes:

import { Controller, Get } from "@nestjs/common";
import {
  AllowAnonymous,
  OptionalAuth,
  Roles,
} from "@thallesp/nestjs-better-auth";

@Controller("users")
export class UserController {
  @Get("public")
  @AllowAnonymous() // Allow anonymous access (no authentication required)
  async publicRoute() {
    return { message: "This route is public" };
  }

  @Get("optional")
  @OptionalAuth() // Authentication is optional for this route
  async optionalRoute(@Session() session: UserSession) {
    return { authenticated: !!session, session };
  }

  @Get("admin")
  @Roles(["admin"]) // Only authenticated users with the 'admin' role can access this route. Uses the access control plugin from better-auth.
  adminRoute() {
    return "Only admins can see this";
  }
}

Alternatively, use it as a class decorator to specify access for an entire controller:

import { Controller, Get } from "@nestjs/common";
import { AllowAnonymous, OptionalAuth } from "@thallesp/nestjs-better-auth";

@AllowAnonymous() // All routes inside this controller are public
@Controller("public")
export class PublicController {
  /* */
}

@OptionalAuth() // Authentication is optional for all routes inside this controller
@Controller("optional")
export class OptionalController {
  /* */
}

@Roles(["admin"]) // All routes inside this controller require 'admin' role. Uses the access control plugin from better-auth.
@Controller("admin")
export class AdminController {
  /* */
}

Hook Decorators

[!IMPORTANT] To use @Hook, @BeforeHook, @AfterHook, set hooks: {} (empty object) in your betterAuth(...) config. You can still add your own Better Auth hooks; hooks: {} (empty object) is just the minimum required.

Minimal Better Auth setup with hooks enabled:

import { betterAuth } from "better-auth";

export const auth = betterAuth({
  basePath: "/api/auth",
  // other better-auth options...
  hooks: {}, // minimum required to use hooks. read above for more details.
});

Create custom hooks that integrate with NestJS's dependency injection:

import { Injectable } from "@nestjs/common";
import {
  BeforeHook,
  Hook,
  AuthHookContext,
} from "@thallesp/nestjs-better-auth";
import { SignUpService } from "./sign-up.service";

@Hook()
@Injectable()
export class SignUpHook {
  constructor(private readonly signUpService: SignUpService) {}

  @BeforeHook("/sign-up/email")
  async handle(ctx: AuthHookContext) {
    // Custom logic like enforcing email domain registration
    // Can throw APIError if validation fails
    await this.signUpService.execute(ctx);
  }
}

Register your hooks in a module:

import { Module } from "@nestjs/common";
import { AuthModule } from "@thallesp/nestjs-better-auth";
import { SignUpHook } from "./hooks/sign-up.hook";
import { SignUpService } from "./sign-up.service";
import { auth } from "./auth";

@Module({
  imports: [AuthModule.forRoot({ auth })],
  providers: [SignUpHook, SignUpService],
})
export class AppModule {}

AuthService

The AuthService is automatically provided by the AuthModule and can be injected into your controllers to access the Better Auth instance and its API endpoints.

import { Controller, Get, Post, Request, Body } from "@nestjs/common";
import { AuthService } from "@thallesp/nestjs-better-auth";
import { fromNodeHeaders } from "better-auth/node";
import type { Request as ExpressRequest } from "express";
import { auth } from "../auth";

@Controller("users")
export class UsersController {
  constructor(private authService: AuthService<typeof auth>) {}

  @Get("accounts")
  async getAccounts(@Request() req: ExpressRequest) {
    // Pass the request headers to the auth API
    const accounts = await this.authService.api.listUserAccounts({
      headers: fromNodeHeaders(req.headers),
    });

    return { accounts };
  }

  @Post("api-keys")
  async createApiKey(@Request() req: ExpressRequest, @Body() body) {
    // Access plugin-specific functionality with request headers
    // createApiKey is a method added by a plugin, not part of the core API
    return this.authService.api.createApiKey({
      ...body,
      headers: fromNodeHeaders(req.headers),
    });
  }
}

When using plugins that extend the Auth type with additional functionality, use generics to access the extended features as shown above with AuthService<typeof auth>. This ensures type safety when using plugin-specific API methods like createApiKey.

Request Object Access

You can access the session and user through the request object:

import { Controller, Get, Request } from "@nestjs/common";
import type { Request as ExpressRequest } from "express";

@Controller("users")
export class UserController {
  @Get("me")
  async getProfile(@Request() req: ExpressRequest) {
    return {
      session: req.session, // Session is attached to the request
      user: req.user, // User object is attached to the request
    };
  }
}

The request object provides:

• req.session: The full session object containing user data and authentication state
• req.user: A direct reference to the user object from the session (useful for observability tools like Sentry)

Advanced: Disable the global AuthGuard

If you prefer to manage guards yourself, you can disable the global guard and then apply @UseGuards(AuthGuard) per controller/route or register it via APP_GUARD.

import { Module } from "@nestjs/common";
import { AuthModule } from "@thallesp/nestjs-better-auth";
import { auth } from "./auth";

@Module({
  imports: [
    AuthModule.forRoot({
      auth,
      disableGlobalAuthGuard: true,
    }),
  ],
})
export class AppModule {}

import { Controller, Get, UseGuards } from "@nestjs/common";
import { AuthGuard } from "@thallesp/nestjs-better-auth";

@Controller("users")
@UseGuards(AuthGuard)
export class UserController {
  @Get("me")
  async getProfile() {
    return { message: "Protected route" };
  }
}

Module Options

When configuring AuthModule.forRoot(), you can provide options to customize the behavior:

AuthModule.forRoot({
  auth,
  disableTrustedOriginsCors: false,
  disableBodyParser: false,
});

The available options are:

| Option | Default | Description | | --------------------------- | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | disableTrustedOriginsCors | false | When set to true, disables the automatic CORS configuration for the origins specified in trustedOrigins. Use this if you want to handle CORS configuration manually. | | disableBodyParser | false | When set to true, disables the automatic body parser middleware. Use this if you want to handle request body parsing manually. | | disableGlobalAuthGuard | false | When set to true, does not register AuthGuard as a global guard. Use this if you prefer to apply AuthGuard manually or register it yourself via APP_GUARD. |