Integrating Okta Authentication in a React-Based Microsoft Office Add-in (Word, Excel, Outlook)

A step-by-step guide to securely adding Okta login to your React Office Add-in for Word, Excel, or Outlook.

Integrating secure authentication into Microsoft Office Add-ins can be tricky — especially when your add-in is built using modern frameworks like React. While most tutorials cover web apps, there’s very little guidance for connecting Okta with Office Add-ins such as Word, Excel, or Outlook. In this article, we’ll walk through the complete process of integrating Okta authentication into a React-based Office Add-in, from configuring your Okta application to handling sign-in flows and securing API access. By the end, you’ll have a working Office Add-in that allows users to sign in using Okta’s enterprise-grade authentication — seamlessly inside Microsoft 365.

What are Microsoft Office Add-in’s?

Microsoft Office Add-ins extend the functionality of familiar Office applications like Word, Excel, Outlook, and PowerPoint by allowing developers to embed web-based experiences directly inside Office. These add-ins run within Office clients across platforms - Windows, macOS, and the web - using standard HTML, CSS, and JavaScript.

Whether it’s automating document workflows, connecting to external l APIs, or simplifying repetitive tasks, Office Add-ins help organizations bring their business logic right where users already work - inside Office 365.

Why Authentication Matters in Enterprise-Grade Add-ins

When your add-in interacts with enterprise systems or user-specific data, authentication becomes essential. You often need to:

• Identify the signed-in user
• Access company APIs or Microsoft Graph data
• Ensure only authorized users perform certain actions

Without proper authentication, your add-in becomes both insecure and unusable in enterprise environments. Modern organizations require Single Sign-On (SSO) and secure token-based authentication mechanisms – which is where Okta comes into play.

Overview of Okta and Why It’s a Great Choice

Okta is a leading identity and access management (IAM) platform trusted by thousands of enterprises. It enables developers to easily add secure, standards-based authentication to any application using protocols like OAuth 2.0 and OpenID Connect (OIDC).

Key reasons why Okta is a great choice for Office Add-ins:

• Supports PKCE (Proof Key for Code Exchange) – ideal for single-page apps like React
• Enterprise-grade SSO – users can log in using existing corporate credentials
• Easy integration – robust SDKs for React (@okta/okta-react and @okta/okta-auth-js)
• Cloud-hosted & scalable – no need to manage authentication servers

By integrating Okta into your React-based Office Add-in, you can provide a seamless, secure login experience while ensuring compliance with enterprise security standards.

Setting Up the React Office Add-in

Using the Yo Office Generator

If you don’t already have a React Office Add-in project, follow these steps:

Install prerequisites (if you haven’t already):

npm install -g yo generator-office

Run the generator:

yo office

Choose options when prompted:

• Project type: React framework
• Add-in type: Task Pane project
• Name your project: e.g., okta-office-addin
• Supported Office application: Word, Excel, or Outlook

Navigate to the project folder and start the dev server:

cd okta-office-addin
npm start

This will start a local server and automatically side load the add-in into Word, Excel, or Outlook (depending on your selection).

Folder Structure Overview

After setup, your project will have a structure similar to this:

okta-office-addin/
│
├── manifest.xml               # Defines your Office Add-in metadata & permissions
├── package.json               # Project dependencies & scripts
├── src/
│   ├── taskpane/
│   │   ├── components/
│   │   │   └── App.jsx        # Main React component for the Add-in UI
│   │   ├── taskpane.html      # Root HTML page loaded inside Office
│   │   └── taskpane.js        # Entry file to bootstrap React
│   ├── assets/                # Icons and static files
│   └── commands/              # Optional: for custom ribbon button commands
│
└── webpack.config.js          # Webpack configuration for bundling

Here’s how the main parts work:

• manifest.xml — tells Office how to load your add-in, which URLs to trust, and what permissions it needs.
• taskpane/ — contains your React UI code (this is where we’ll integrate Okta).
• commands/ — defines background commands for buttons or custom actions.

Once the setup is done, you can run: Run the Add-in locally using two terminals:

• Start Webpack dev server: npm start dev-server
• Start HTTPS server for Office: npm start

Word will open automatically, and you’ll find your Add-in available in the toolbar. To stop the HTTPS server use below command:

npm stop

Configuring Okta for Your Add-in

Before integrating Okta into your React Office Add-in, you’ll need to set up an Okta application in your Okta Developer Console. This will allow your add-in to authenticate users and obtain tokens securely.

Step 1: Create an Okta Developer Account If your organization already uses Okta Enterprise, you can use your company’s Okta domain. Otherwise, create a free Okta developer account at developer.okta.com.

Step 2: Create a New Okta Application From the Okta dashboard, go to Applications → Create App Integration Choose the following options:

• Sign-in method: OIDC — OpenID Connect
• Application type: Single-Page Application (SPA) Then, Click Next

Step 3: Configure App Settings

• App name: React Office Add-in (or any name you prefer)
• Grant type: Authorization Code with PKCE (enabled by default for SPAs)
• Sign-in redirect URIs (for local dev):

https://localhost:3000/login/callback
https://localhost:3000/auth.html

Step 4: Copy Okta Configuration Details

Once the app is created, copy the following values from the General tab:

• Client ID: e.g., 0oa123xyz...
• Issuer: e.g., [https://dev-xxxx.okta.com/oauth2/default](https://dev-xxxx.okta.com/oauth2/default)
• Redirect URI: [https://localhost:3000/login/callback](https://localhost:3000/login/callback)

Tip: The /oauth2/default at the end of your issuer URL refers to the default authorization server. For SPAs like React Add-ins, PKCE ensures secure token exchange.

Integrating Okta with React

We’ll use two official Okta libraries:

• @okta/okta-react
• @okta/okta-auth-js

Install them using:

npm install @okta/okta-react @okta/okta-auth-js

Step 1: Create oktaConfig.js

Inside your project’s src folder, create a file named oktaConfig.js and add the following:

import { OktaAuth } from '@okta/okta-auth-js';
const oktaConfig = {
  clientId: "{client_id}",
  issuer: "https://{your_company}.okta.com",
  redirectUri: "https://localhost:3000/auth.html",
  scopes: ["openid", "profile", "email"],
  pkce: true,
  storageManager: {
    token: { storageTypes: ['sessionStorage', 'localStorage', 'cookie'] as any }
  }
};
let oktaAuth: any;
try {
  oktaAuth = new OktaAuth(oktaConfig);
  // Custom popup-based login
  oktaAuth.signInWithRedirect = () => {
    sessionStorage.removeItem('okta-pkce-storage');
    localStorage.removeItem('okta-pkce-storage');
    const popup = window.open(
      '/auth.html?mode=popup&t=' + Date.now(),
      'okta-auth-popup',
      'width=500,height=700,scrollbars=yes,resizable=yes,' +
      'left=' + (window.screenX + (window.outerWidth - 500) / 2) +
      ',top=' + (window.screenY + (window.outerHeight - 700) / 2)
    );
    if (!popup) throw new Error('Popup blocked - please allow popups for this site');
    popup.focus();
    return Promise.resolve();
  };
} catch (error) {
  console.error('Okta initialization failed:', error);
  oktaAuth = {
    signInWithRedirect: () => Promise.reject(new Error('Okta not initialized')),
    signOut: () => Promise.reject(new Error('Okta not initialized')),
    authStateManager: { getAuthState: () => ({ isAuthenticated: false, isPending: false }), subscribe: (cb: any) => { setTimeout(() => cb({ isAuthenticated: false, isPending: false }), 0); return () => {}; }, updateAuthState: () => Promise.resolve() },
    tokenManager: { setTokens: () => Promise.resolve(), get: () => Promise.resolve(null), clear: () => Promise.resolve() }
  };
}
export { oktaAuth };

Note: Replace {yourOktaDomain} with your Okta URL and the {client_id}.

Step 2: Wrap Your App with the Security Component

Open your main app file (e.g., App.tsx) and copy paste the below code:

import React from 'react';
import { MemoryRouter, Routes, Route } from 'react-router-dom';
import { Security, LoginCallback } from '@okta/okta-react';
import { oktaAuth } from '../../config/OktaConfig';
import Home from './Home';
import ErrorBoundary from './ErrorBoundary';
interface AppProps {
  title?: string;
}
const App: React.FC<AppProps> = ({ title }) => {
  const restoreOriginalUri = async (_oktaAuth: any, _originalUri: string): Promise<void> => {
    return Promise.resolve();
  };
  return (
    <ErrorBoundary>
      <MemoryRouter>
        <Security 
          oktaAuth={oktaAuth}
          restoreOriginalUri={restoreOriginalUri}
        >
          <Routes>
            <Route path="/" element={<Home title={title} />} />
            <Route path="/login/callback" element={<LoginCallback />} />
          </Routes>
        </Security>
      </MemoryRouter>
    </ErrorBoundary>
  );
};
export default App;

Why we can’t use BrowserRouter in Office Add-ins

Office Add-ins run inside a task pane, which is essentially a sandboxed iframe embedded in Word, Excel, or Outlook. Unlike normal web apps, the add-in cannot control the browser URL, and navigating via BrowserRouter would break routing or even the add-in UI. Instead, we use MemoryRouter, which keeps routing in memory without relying on the URL, making it fully compatible with Office Add-ins.

Step 3: Handling Login and Protected Routes

The Security component automatically protects routes wrapped with SecureRoute. If the user isn’t logged in, they’ll be redirected to the Okta sign-in page. Once authenticated, Okta redirects the user back to your app via the /login/callback route, which the LoginCallbackcomponent handles.

At this point: Your React Add-in is fully connected to Okta — users can log in securely, and protected routes are handled automatically.

Handling Okta Authentication in Office Add-ins: Pop-up Flow

In traditional web apps, Okta redirects the user back to the same page after login. However, in an Office Add-in task pane (Word, Excel, or Outlook), redirecting the whole task pane to a browser breaks the add-in context. Once the add-in is redirected outside, the user cannot return automatically.

The solution: perform authentication in a popup window. This way:

• The main add-in UI stays intact.
• The popup handles Okta login and token retrieval.
• Tokens are securely passed back to the task pane via window.postMessage.

Step 1: Create auth.html

In your project’s root folder, create auth.html:

<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>Okta Auth Popup</title>
</head>
<body>
  <script src="https://global.oktacdn.com/okta-auth-js/7.4.2/okta-auth-js.min.js"></script>
  <script>
    const oktaAuth = new OktaAuth({
      clientId: "YOUR_CLIENT_ID",
      issuer: "https://{yourOktaDomain}/oauth2/default",
      redirectUri: window.location.origin + "/auth.html",
      scopes: ["openid", "profile", "email"],
      pkce: true,
      storageManager: { token: { storageTypes: ["sessionStorage"] } }
    });
    const isPopup = window.opener !== null;
    if (oktaAuth.isLoginRedirect()) {
      oktaAuth.handleLoginRedirect()
        .then(tokens => {
          if (isPopup) {
            window.opener.postMessage({ type: "OKTA_AUTH_SUCCESS", tokens }, window.location.origin);
            window.close();
          } else window.location.href = "/";
        })
        .catch(err => {
          if (isPopup) {
            window.opener.postMessage({ type: "OKTA_AUTH_ERROR", error: err.message }, window.location.origin);
            window.close();
          } else console.error("Authentication error:", err);
        });
    } else oktaAuth.signInWithRedirect();
  </script>
</body>
</html>

Note: This replaces the minimal redirect HTML. It ensures Okta login works in a popup and tokens can return to the task pane.

Step 2: Configure Webpack to Serve auth.html

In your webpack.config.js, include auth.html in the CopyWebpackPlugin section:

new CopyWebpackPlugin({
  patterns: [
    {
      from: "assets/*",
      to: "assets/[name][ext][query]",
    },
    {
      from: "auth.html",  // Correct - root level
      to: "auth.html",
    },
    // ... other patterns
  ],
}),

This makes auth.html available at https://localhost:3000/auth.html during development — a critical step for Okta redirects inside Office.

Step 3: Add Redirect URI in Okta

Go back to your Okta Developer Console → Application Settings, and make sure the following redirect URIs are added:

• [https://localhost:3000/login/callback](https://localhost:3000/login/callback)
• [https://localhost:3000/auth.html](https://localhost:3000/auth.html)

The second URI (/auth.html) allows Okta to complete the sign-in flow when your add-in runs inside Word or Excel.

Note: For enterprise Okta, replace the domain with your org’s Okta URL.

Handling Tokens from the Popup in Your Task Pane

After the user logs in through the popup (auth.html), the tokens (ID token, access token) are sent back to the main task pane via window.postMessage. You need to listen for these messages and store the tokens using your oktaAuth instance.

Step 1: Add a Message Listener in Home.tsx or Your Main Component

import { useEffect } from 'react';
import { oktaAuth } from '../../config/OktaConfig';
const Home: React.FC = () => {
  useEffect(() => {
    const handleOktaMessage = (event: MessageEvent) => {
      if (event.origin !== window.location.origin) return;
      const { type, tokens, error } = event.data;
      if (type === 'OKTA_AUTH_SUCCESS' && tokens) {
        oktaAuth.tokenManager.setTokens(tokens);
        console.log('User logged in successfully', tokens);
      } else if (type === 'OKTA_AUTH_ERROR') {
        console.error('Okta login error', error);
      }
    };
    window.addEventListener('message', handleOktaMessage);
    return () => window.removeEventListener('message', handleOktaMessage);
  }, []);
  return (
    <div>
      <h1>Welcome to your Office Add-in!</h1>
      <button onClick={() => oktaAuth.signInWithRedirect()}>Login with Okta</button>
    </div>
  );
};
export default Home;

How This Works:

1. Popup sends tokens → window.postMessage({ type: 'OKTA_AUTH_SUCCESS', tokens })
2. Task pane receives tokens → Listener stores them using oktaAuth.tokenManager.setTokens()
3. User is now authenticated → You can access oktaAuth.tokenManager.get('accessToken') or get('idToken') for API calls.

Testing the Add-in

Once your popup-based Okta authentication is set up, verify it works inside the Office Add-in:

1. Running the Add-in in Word or Excel Start your development servers:

npm start dev-server   # Webpack dev server 
npm start              # Local HTTPS server for Office

Open Word or Excel, and your add-in should appear in the ribbon under the task pane.

2. Verifying the Login Flow

• Click the Login with Okta button in your task pane.
• A popup should appear prompting the user to sign in.
• After successful login, the popup closes automatically, and the tokens are sent back to the main task pane.
• Check the console log in your task pane (oktaAuth.tokenManager.getTokens()) to confirm the ID and access tokens are stored correctly.

3. Debugging Common Issues

• CORS Errors: Ensure your API server or Okta redirect URIs allow requests from [https://localhost:3000.](https://localhost:3000.)
• Redirect URI Mismatch: Verify that both https://localhost:3000/login/callback and https://localhost:3000/auth.html are registered in your Okta application.
• Popup Blocked: Make sure the browser allows popups for localhost.
• Task Pane Reloads: Tokens are stored in sessionStorage, localStorage, or cookies (based on your storageManager) to survive reloads.

Tip: Use the browser developer console inside the task pane to inspect logs and token values. This is the fastest way to verify the popup authentication flow.

Conclusion

Integrating Okta authentication into a React-based Microsoft Office Add-in can seem challenging at first, but with the right approach, it becomes straightforward and secure. By using a popup-based login flow, you ensure that users stay within the add-in context while signing in, avoiding the common issue of being redirected to the browser and breaking the task pane experience.

Leveraging Okta’s PKCE-enabled SPA authentication and React libraries like @okta/okta-react and @okta/okta-auth-js allows your add-in to securely authenticate users, access company APIs, and maintain enterprise-grade security standards.

With this setup, your Office Add-in is not only functional but also compliant with modern identity management best practices, providing a seamless login experience for users across Word, Excel, and Outlook. Further enhancements like API integration with access tokens, token refresh handling, and user-friendly error messages can be implemented to extend functionality and improve user experience.