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 >= 1.5.0. Older versions are deprecated and unsupported.

Before you start, make sure you have:

• A working NestJS application
• Better Auth (>= 1.5.0) 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, {
    // The library will re-add the default body parsers for non-auth routes.
    bodyParser: false,
  });
  await app.listen(process.env.PORT ?? 3333);
}
bootstrap();

[!IMPORTANT] Side Effect: Since we disable NestJS's built-in body parser, the rawBody: true option in NestFactory.create() has no effect. If you need access to req.rawBody (e.g., for webhook signature verification), use bodyParser.rawBody in AuthModule.forRoot() instead. See Module Options for details.

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,
      bodyParser: {
        json: { limit: "2mb" },
        urlencoded: { limit: "2mb", extended: true },
        rawBody: true,
      },
    }),
  ],
})
export class AppModule {}

Both bodyParser.json and bodyParser.urlencoded accept parser options plus an enabled flag if you want to disable either parser individually. Set bodyParser.rawBody to true if you also want Nest-style req.rawBody support.

On Fastify, bodyParser.urlencoded with extended: true uses the optional peer dependency qs. Install qs in your application if you want nested URL-encoded parsing there.

If you configure trustedOrigins, this module also applies Better Auth CORS headers for auth routes. On Fastify, Better Auth routes are mounted through middleware, so app-level @fastify/cors does not fully cover them by itself.

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 and OptionalAuth Decorators

Control authentication requirements for specific routes:

import { Controller, Get } from "@nestjs/common";
import { AllowAnonymous, OptionalAuth } 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 };
  }
}

Alternatively, use as a class decorator for an entire controller:

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

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

Role-Based Access Control

This library provides two role decorators for different use cases:

| Decorator | Checks | Use Case | |-----------|--------|----------| | @Roles() | user.role only | System-level roles (admin plugin) | | @OrgRoles() | Organization member role only | Organization-level roles (organization plugin) |

[!IMPORTANT] These decorators are intentionally separate to prevent privilege escalation. The @Roles() decorator only checks user.role and does not check organization member roles. This ensures an organization admin cannot bypass system-level admin protection.

@Roles() - System-Level Roles

Use @Roles() for system-wide admin protection. This checks only the user.role field from Better Auth's admin plugin.

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

@Controller("admin")
export class AdminController {
  @Roles(["admin"])
  @Get("dashboard")
  async adminDashboard() {
    // Only users with user.role = 'admin' can access
    // Organization admins CANNOT access this route
    return { message: "System admin dashboard" };
  }
}

// Or as a class decorator
@Roles(["admin"])
@Controller("admin")
export class AdminController {
  /* All routes require user.role = 'admin' */
}

@OrgRoles() - Organization-Level Roles

Use @OrgRoles() for organization-scoped protection. This checks only the organization member role and requires an active organization (activeOrganizationId in session).

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

@Controller("org")
export class OrgController {
  @OrgRoles(["owner", "admin"])
  @Get("settings")
  async getOrgSettings(@Session() session: UserSession) {
    // Only org owners/admins can access (requires activeOrganizationId)
    // System admins (user.role = 'admin') CANNOT access without org context
    return { orgId: session.session.activeOrganizationId };
  }

  @OrgRoles(["owner"])
  @Get("billing")
  async getOrgBilling() {
    // Only org owners can access
    return { message: "Billing settings" };
  }
}

[!NOTE] Both role decorators accept any role strings you define. Better Auth's organization plugin provides default roles (owner, admin, member), but you can configure custom roles. The organization creator automatically gets the owner role.

Permission-Based Access Control

This library provides two permission decorators for fine-grained access control:

| Decorator | Checks | Use Case | |-----------|--------|----------| | @UserHasPermission() | User-level permissions | System-level permissions (admin plugin access control) | | @MemberHasPermission() | Organization member permissions | Organization-level permissions (organization plugin access control) |

@UserHasPermission() - System-Level Permissions

Use @UserHasPermission() for system-wide permission-based access control. This checks user permissions using Better Auth's admin plugin access control.

Prerequisites:

• Configure access control in your Better Auth admin plugin

import { betterAuth } from "better-auth";
import { admin } from "better-auth/plugins/admin";
import { createAccessControl } from "better-auth/plugins/access";

const statement = {
  project: ["create", "share", "update", "delete"],
  sale: ["create", "read", "update", "delete"],
} as const;

const ac = createAccessControl(statement);

const editor = ac.newRole({
  project: ["create", "update"],
});

const admin = ac.newRole({
  project: ["create", "update", "delete"],
  sale: ["create", "read", "update", "delete"],
});

export const auth = betterAuth({
  plugins: [
    admin({
      ac,
      roles: {
        editor,
        admin,
      },
    }),
  ],
});

Usage:

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

@Controller("projects")
export class ProjectController {
  @UserHasPermission({ permission: { project: ["create", "update"] } })
  @Post()
  async createProject() {
    // Only users with project: ["create", "update"] permissions can access
    return { message: "Project created" };
  }

  @UserHasPermission({ permission: { project: ["delete"] } })
  @Post(":id/delete")
  async deleteProject() {
    // Only users with project: ["delete"] permission can access
    return { message: "Project deleted" };
  }

  @UserHasPermission({
    permissions: { project: ["create"], sale: ["create"] },
  })
}

Options:

• permission: A single permission check (e.g., { project: ["create", "update"] })
• permissions: Multiple permission checks across resources (e.g., { project: ["create"], sale: ["create"] })
• role (server-only): Check permissions for a specific role
• userId (optional): Check permissions for a specific user (defaults to current user)

@MemberHasPermission() - Organization-Level Permissions

Use @MemberHasPermission() for organization-scoped permission-based access control. This checks organization member permissions using Better Auth's organization plugin access control. Requires an active organization (activeOrganizationId in session).

Prerequisites:

• Configure access control in your Better Auth organization plugin
• Define custom organization roles with permissions

import { betterAuth } from "better-auth";
import { organization } from "better-auth/plugins/organization";
import { createAccessControl } from "better-auth/plugins/access";

const statement = {
  project: ["create", "share", "update", "delete"],
  sale: ["create", "read", "update", "delete"],
  organization: ["update", "delete"],
} as const;

const ac = createAccessControl(statement);

const editor = ac.newRole({
  project: ["create", "update"],
});

const admin = ac.newRole({
  project: ["create", "update", "delete"],
  organization: ["update"],
});

export const auth = betterAuth({
  plugins: [
    organization({
      ac,
      roles: {
        editor,
        admin,
      },
    }),
  ],
});

Usage:

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

@Controller("org/projects")
export class OrgProjectController {
  @MemberHasPermission({ permissions: { project: ["create", "update"] } })
  @Post()
  async createProject(@Session() session: UserSession) {
    // Only org members with project: ["create", "update"] permissions can access
    // Requires activeOrganizationId in session
    return {
      message: "Project created",
      orgId: session.session.activeOrganizationId,
    };
  }

  @MemberHasPermission({ permissions: { project: ["delete"] } })
  @Post(":id/delete")
  async deleteProject() {
    // Only org members with project: ["delete"] permission can access
    return { message: "Project deleted" };
  }
}

Options:

• permissions: The permissions to check (required). Must match the structure in your organization access control.

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 {}

Database Hook Decorators

[!IMPORTANT] To use @DatabaseHook, @BeforeCreate, @AfterCreate, @BeforeUpdate, @AfterUpdate, @BeforeDelete, @AfterDelete, set databaseHooks: {} (empty object) in your betterAuth(...) config.

Database hooks let you hook into the lifecycle of core database operations (create, update, delete) for Better Auth models (user, session, account, verification).

Minimal Better Auth setup with database hooks enabled:

import { betterAuth } from "better-auth";

export const auth = betterAuth({
  // other better-auth options...
  databaseHooks: {}, // empty object is the minimum required
});

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

import { Injectable } from "@nestjs/common";
import {
  DatabaseHook,
  BeforeCreate,
  AfterCreate,
} from "@thallesp/nestjs-better-auth";
import { EmailService } from "./email.service";

@DatabaseHook()
@Injectable()
export class UserCreateHook {
  constructor(private readonly emailService: EmailService) {}

  @BeforeCreate("user")
  async beforeUserCreate(user) {
    return {
      data: {
        ...user,
        firstName: user.name.split(" ")[0],
        lastName: user.name.split(" ")[1],
      },
    };
  }

  @AfterCreate("user")
  async afterUserCreate(user) {
    await this.emailService.sendWelcomeEmail(user.email);
  }
}

Register your database hooks in a module:

import { Module } from "@nestjs/common";
import { AuthModule } from "@thallesp/nestjs-better-auth";
import { UserCreateHook } from "./hooks/user-create.hook";
import { EmailService } from "./email.service";
import { auth } from "./auth";

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

Available method decorators:

| Decorator | Description | |-----------|-------------| | @BeforeCreate(model) | Runs before a record is created | | @AfterCreate(model) | Runs after a record is created | | @BeforeUpdate(model) | Runs before a record is updated | | @AfterUpdate(model) | Runs after a record is updated | | @BeforeDelete(model) | Runs before a record is deleted | | @AfterDelete(model) | Runs after a record is deleted |

Where model is one of: "user", "session", "account", "verification".

before hooks can return false to abort the operation, or { data: ... } to modify the data before it's written. after hooks are for side effects only.

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,
  bodyParser: {
    json: { enabled: true },
    urlencoded: { enabled: true, extended: true },
    rawBody: false,
  },
  disableBodyParser: false,
  enableRawBodyParser: false,
  disableGlobalAuthGuard: false,
  disableControllers: 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. On Fastify, use this only if you want to fully manage Better Auth route CORS yourself. | | bodyParser | Re-adds JSON and URL-encoded body parsers | Configure the body parsers re-added by the module after Nest body parsing is disabled. json and urlencoded accept the parser options object plus enabled?: boolean, and rawBody?: boolean enables req.rawBody. | | disableBodyParser | false | Deprecated. Use bodyParser.json.enabled and bodyParser.urlencoded.enabled instead. When set to true, disables both parsers unless you explicitly re-enable one in bodyParser. | | enableRawBodyParser | false | Deprecated. Use bodyParser.rawBody instead. When set to true, enables raw body parsing and attaches the raw buffer to req.rawBody. | | 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. | | disableControllers | false | When set to true, does not register any controllers. Use this if you want to handle routes manually. | | middleware | undefined | Optional middleware function that wraps the Better Auth handler. Receives (req, res, next) parameters. Useful for integrating with request-scoped libraries like MikroORM's RequestContext. |

Body Parser Configuration

Use bodyParser to customize the parsers that this library re-adds after you disable Nest's built-in body parser:

AuthModule.forRoot({
  auth,
  bodyParser: {
    json: {
      limit: "2mb",
    },
    urlencoded: {
      enabled: true,
      extended: true,
      limit: "2mb",
    },
    rawBody: true,
  },
});

bodyParser.rawBody enables req.rawBody support, while bodyParser.json and bodyParser.urlencoded configure the corresponding parser behavior for the active adapter.

If you use Fastify with bodyParser.urlencoded({ extended: true }), install the optional peer dependency qs to enable nested form parsing.

CORS on Fastify

If your Better Auth config sets trustedOrigins, this module applies CORS to Better Auth routes automatically.

On Fastify, Better Auth routes are served through middleware internally. Because of that:

• app-level @fastify/cors does not fully apply to Better Auth routes on its own
• this module applies Better Auth route CORS from trustedOrigins

This Fastify fallback only supports array-based trustedOrigins. Function-based trustedOrigins remain unsupported unless you set disableTrustedOriginsCors: true and manage Better Auth route CORS manually.

Set disableTrustedOriginsCors: true only if you want to fully manage Better Auth route CORS yourself.

Using Custom Middleware

You can provide a custom middleware function that wraps the Better Auth handler. This is particularly useful when integrating with libraries like MikroORM that require request context:

import { RequestContext } from '@mikro-orm/core';

AuthModule.forRoot({
  auth,
  middleware: (req, res, next) => {
    RequestContext.create(orm.em, next);
  },
});

The middleware receives standard Express middleware parameters (req, res, next) where next is a function that invokes the Better Auth handler.