Introduction to Auth0 Actions

Aaishika S Bhattacharya
7 min readJan 15, 2022


Actions are used to customize and extend Auth0’s capabilities with custom logic, read on to see how you can implement it effortlessly in your project.

What are Auth0 Actions?

Actions are secure, tenant-specific, versioned functions written in Node.js that execute at certain points during the Auth0 runtime. In short, an Action is a programmatic way to add custom business logic into your login flow. With Actions, you can add a customized mandatory logic to your login and identity flows that satiate your needs. The service also allows you to connect external integrations that complement the overall extensibility experience.

In the aforementioned flow, you can observe that as the user tries logging into the system, a trigger is initiated to verify the user’s identity using Onfido, and then the user’s consent is confirmed using OneTrust before completing the login flow and issuing the token.

Why Auth0 Actions?

  • Observability: When Actions are executed, Auth0 will capture key metrics about them and link them to Auth0 Logs.
  • Extensibility: Auth0 Actions is built to give developers more tooling and a better experience in their login workflows.
  • Multiple actions on every trigger: Every Action trigger supports multiple independent Actions.
  • Version Control: You have the ability to store a history of individual Action changes and the power to revert back to previous versions as needed.
  • Access to NPM Packages: Nearly all public NPM packages are available to be used within Actions.
  • Pre-Production Testing: Your personal Actions can be drafted, reviewed, and tested before deploying into production.
  • Improved Developer Experience: The flow editor lets you visually build custom workflows with drag and drop Action blocks for complete control.


We will be creating an Auth0 Action similar to the flow we saw at the beginning of this article using React. We’ll basically be creating an Action to make Multi-Factor Authentication (MFA) mandatory. You’ll need the following:

  1. An Auth0 Account (if you don’t have one yet, visit this link and create one for free)
  2. Any Code Editor of your choice. I’d recommend Visual Studio Code.

Getting Started with Auth0

  1. Assuming that you already have an Auth0 Account, scroll down to find the option that says “Create Application”.

2. In the modal that follows, add the name of the application and then select Single Page Web Applications as its type.

3. Click the Create button which will redirect you to the “Quick start” section. In the new modal, select “React”.

4. You should see a screen that’s similar to the one below. Proceed to download the code selecting the appropriate option.

5. Click on the Setting tab to change the configuration of your Auth0 application. We’ll also be borrowing some data from this tab, precisely the Domain, and Client ID. I won’t be covering the theory of different URLs and origins but if you are interested in reading more about them, refer to this similar article that I drafted a while back.

6. Add your localhost URL which will be http://localhost:3000 unless you have changed it, to the following fields in the Settings Page.

  • Allowed Callback URLs
  • Allowed Logout URLs
  • Allowed Web Origins

Setting Up Users and Roles

  1. Click on the User Management Tab in the sidebar. Click on the Users tab followed by the Create User Option. We’ll create 2 Users for our Action.

2. Now go to the Roles Tab and click on Create Role Button. We’ll name the role Admin. Once created go to the user tab and assign it to the Admin user we created previously.

We are through with setting up roles and users. Now let’s return to our actual Application.

Setting Up the React App

  1. Unzip the file we downloaded a while back and open the folder in a code editor of your choice. In src/auth_config.json add the details of your application from the Auth0 Dashboard, specifically the domain and Client ID.
  2. To run the code, we first need to install the dependencies. Execute npm installfor the same. Execute the following to run the application in development mode npm run dev. You’ll see a Single Page Application like the one below built using React.

You can choose to log in using the credentials we created for Users.

Setting Up Actions

Setting up Actions is easy.

  1. Click on the Actions tab in the sidebar towards your left. Go to the Flows Category to set up the flow of our Login. Select Login Flow. This will run the flow of action once the trigger is executed.

2. Click on the + Button in front of Add Action and select Build Custom. Add a name, leave everything else as is and click on Create.

Once done, you’re redirected to a screen that looks like the one below:

3. Find the onExecutePostLogin function and add the following snippet to it:

if (event.authorization != undefined && event.authorization.roles.includes("Admin")) {

What this simply does is verify if the user has an Admin role and if in case it does, asks the User to go through MFA. On the left side of the code editor, you can see a play button that will emulate a testing environment for your action. You will find the event object in which you can test the actions flow by adding Admin to the authorization.roles array.

When you run the function with an Admin role, you will see a response as follows and when it’s not present you get an empty array.

4. Click on Save Draft followed by Deploy. Now go back to the flow and click on the Custom tab towards the right and you will be able to drag and drop the Authentication Action into the flow. Click on Apply and the new flow will be integrated into your Application.

5. Now we need to enable Multi-Factor Authenticationin the Auth0 dashboard. In the Security Tab that you can find in the sidebar, choose Multi-factor Auth. In the following screen enable One-time Password. This will allow users to use applications like Google Authenticator for a one-time password. There are other factors as well that you can enforce such as SMS or Email-based OTP.

In the Define Policiessection leave everything as is and save.

Running the Application

No spoilers here. Just hit npm startand you’re all set. When you try to login into the Application with the Admin account, you’ll be asked to complete the MFA flow we created.

You’ll basically be asked to consent to share your data with the Application and will only be allowed to proceed further after you share the required things. Try to log in with both the users we created previously to see the difference. The Action we created checks if the user trying to log in has the Admin role and if so, it triggers an MFA workflow with any of the enabled MFA use cases of the tenant.

Ending Notes

In a few steps, this is how we can effectively boost the security of our Application using Auth0 Actions. If you are interested in knowing more about the different sorts of triggers, head over to this link. You can also find the official documentation right here.

This article is based upon the following blog post — How to Extend Your Login Flow with Auth0 Actions, drafted by Rohit Mathew, a fellow Auth0 Ambassador.

Implementing Auth0 is relatively easy in comparison to other services available in the market, which is why I prefer working with it. In case of any doubts or queries, please feel free to open a discussion below.



Aaishika S Bhattacharya

Jr. Developer Advocate @DigitalOcean 🥑 ∘ Team @Hacktoberfest 👨🏻‍💻 ∘ @Github Campus Expert 🚩 ∘ Design + Code + Git 🛠️