NestJS Integration - Better Auth

This guide will show you how to integrate Better Auth with NestJS.

Before you start, make sure you have a Better Auth instance configured. If you haven't done that yet, check out the installation.

<Callout type="info"> The NestJS integration is **community maintained**. If you encounter any issues, please open them at [nestjs-better-auth](https://github.com/ThallesP/nestjs-better-auth). </Callout>

Installation

Install the NestJS integration library:

package-install

@thallesp/nestjs-better-auth

Basic Setup

<Callout type="warn"> Currently the library has beta support for Fastify, if you experience any issues with it, please open an issue at [nestjs-better-auth](https://github.com/ThallesP/nestjs-better-auth). </Callout>

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, {
    bodyParser: false, // Required for Better Auth
  });
  await app.listen(process.env.PORT ?? 3000);
}
bootstrap();

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"; // Your Better Auth instance

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

3. Route Protection

Global by default: An AuthGuard is registered globally by this module. All routes are protected unless you explicitly allow access.

Use the Session decorator to access the user session:

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

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

  @Get('public')
  @AllowAnonymous() // Allow anonymous access
  async getPublic() {
    return { message: 'Public route' };
  }

  @Get('optional')
  @OptionalAuth() // Authentication is optional
  async getOptional(@Session() session: UserSession) {
    return { authenticated: !!session };
  }
}

Full Documentation

For comprehensive documentation including decorators, hooks, global guards, and advanced configuration, visit the NestJS Better Auth repository.