How to implement Auth0 to your Express back-end API

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In today’s interconnected world, security is paramount, especially when handling sensitive data. With the proliferation of web applications, ensuring that only authorized users can access protected resources is crucial. In this tutorial, we’ll explore how to fortifying your Express.js backend API with Auth0 security measures, allowing only authenticated users from a React.js frontend to access sensitive endpoints.

Introduction to Authentication and Authorization

Authentication is the process of verifying the identity of a user, ensuring that they are who they claim to be. Authorization, on the other hand, determines what actions a user is allowed to perform once they have been authenticated. Together, authentication and authorization form the foundation of a secure web application, protecting sensitive data and resources from unauthorized access.

Let’s start by creating the main directory structure for your Express.js backend.

First, create a directory for your project. You can name it whatever you like, but for this example, let’s call it express-backend.

Navigate to the Directory:

Initialize npm Package:

Setting Up Dependencies

Before we dive in, let’s set up our project by installing the essential dependencies. As we’ll be leveraging Express.js for our backend and integrating Auth0 for authentication, we’ll need to install the following packages: express, express-oauth2-jwt-bearer, and cors for handling cross-origin resource sharing. Let’s proceed with the installation.

Create a file named server.js in your project directory. This file will serve as the entry point for your Express.js application.

Once you’re done installing dependencies and creating server.js, you can use the following command to open it in VSCode:

Configuring Auth0

  • Sign Up/Login to Auth0: If you haven’t already, sign up for an Auth0 account or log in to your existing one.
  • Create an API: Once logged in, navigate to Applications and then to APIs section in the Auth0 dashboard and click on the “Create API” button.
  • Fill in API Information: Provide a name for your API, such as “My Express.js Backend API,” and set an identifier (audience). This identifier will be used by Auth0 to recognize your API. It’s typically in URL format, like
  • Choose Token Settings: Under the “Signing Algorithm” section, select the appropriate algorithm based on your preferences. Auth0 supports RS256 by default, which is recommended for most use cases.
  • Define Scopes (Optional): You can define scopes to restrict access to certain parts of your API. This step is optional but useful for fine-grained access control.
  • Save Changes: Once you’ve filled in the necessary information, click on the “Create” button to save your API settings.

Implementing Authentication Middleware

With Auth0 configured, let’s implement authentication middleware in our Express.js backend to validate JWT tokens issued by Auth0. Create a file named authMiddleware.js:

Replace <YOUR_API_IDENTIFIER> with the identifier for your API audience, <YOUR_AUTH0_DOMAIN> with your Auth0 domain and <YOUR_SIGNING_ALGORITHM> with your signing algorithm.

Creating API Endpoints

Now, let’s define our API endpoints in server.js:

ReactJS logo

Integrating with React.js Frontend

To demonstrate integration with a React.js frontend, let’s create a simple component that fetches data from our secured backend endpoint.


In this tutorial, we’ve learned how to secure an Express.js backend with Auth0 for authentication. By integrating Auth0’s authentication platform and implementing JWT-based authentication middleware, we’ve created a robust authentication system that ensures only authorized users can access protected endpoints. Additionally, we’ve demonstrated how to integrate our secured backend with a React.js frontend, enabling seamless communication between the two.

With this setup, you can confidently build and deploy web applications that prioritize security without sacrificing usability. By leveraging Auth0 and Express.js, you can create secure authentication systems that protect sensitive data and provide a seamless user experience.

Source code


Secure Your ReactJS App with Auth0 Authentication

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