For our new friends:

Every app needs authentication and authorization. Logto is an Auth0 alternative designed for modern apps and SaaS products.

In this article, we will go through the steps to quickly build the Kakao sign-in experience (user authentication) with Express and  Logto.

Prerequisites

• A running Logto instance. Check out the introduction page to get started.
• Basic knowledge of Express.
• A usable Kakao account.

Create an application in Logto

In you browser, open a new tab and enter the link of Logto Admin Console.

Once the page is loaded, in the "Get Started" section click the View all link to open the application framework list page.

Choose your application type

In the opening modal, scroll to the "Traditional web" section or filter all the available " Traditional web" frameworks using the quick filter checkboxes on the left.

Click the "Express" framework card to start creating your application.

Enter application name

Enter the application name, e.g., "Bookstore," and click "Create application."

🎉 Ta-da! You just created your first application in Logto. You'll see a congrats page which includes a detailed integration guide. Follow the guide to see what the experience will be in your application.

Integrate Logto SDK

tip:

• The sample project is available on our SDK repository.

Installation

Install Logto SDK via your favorite package manager:

npm

npm i @logto/express cookie-parser express-session

pnpm

pnpm add @logto/express cookie-parser express-session

yarn

yarn add @logto/express cookie-parser express-session

Integration

Prepare configs and required middlewares

Prepare configuration for the Logto client:

app.ts

import { LogtoExpressConfig } from '@logto/express';

const config: LogtoExpressConfig = {
  appId: '<your-application-id>',
  appSecret: '<your-application-secret>',
  endpoint: '<your-logto-endpoint>', // E.g. http://localhost:3001
  baseUrl: '<your-express-app-base-url>', // E.g. http://localhost:3000
};

The SDK requires express-session to be configured in prior.

app.ts

import cookieParser from 'cookie-parser';
import session from 'express-session';

app.use(cookieParser());
app.use(
  session({
    secret: 'random_session_key', // Replace with your own secret
    cookie: { maxAge: 14 * 24 * 60 * 60 * 1000 }, // In miliseconds
  })
);

Configure redirect URIs

Before we dive into the details, here's a quick overview of the end-user experience. The sign-in process can be simplified as follows:

1. Your app invokes the sign-in method.
2. The user is redirected to the Logto sign-in page. For native apps, the system browser is opened.
3. The user signs in and is redirected back to your app (configured as the redirect URI).

Regarding redirect-based sign-in

1. This authentication process follows the OpenID Connect (OIDC) protocol, and Logto enforces strict security measures to protect user sign-in.
2. If you have multiple apps, you can use the same identity provider (Logto). Once the user signs in to one app, Logto will automatically complete the sign-in process when the user accesses another app.

To learn more about the rationale and benefits of redirect-based sign-in, see Logto sign-in experience explained.

---

note:

In the following code snippets, we assume your app is running on http://localhost:3000/.

Configure redirect URIs

Switch to the application details page of Logto Console. Add a redirect URI http://localhost:3000/callback.

Just like signing in, users should be redirected to Logto for signing out of the shared session. Once finished, it would be great to redirect the user back to your website. For example, add http://localhost:3000/ as the post sign-out redirect URI section.

Then click "Save" to save the changes.

Register routes

The SDK provides a helper function handleAuthRoutes to register 3 routes:

1. /logto/sign-in: Sign in with Logto.
2. /logto/sign-in-callback: Handle sign-in callback.
3. /logto/sign-out: Sign out with Logto.

Add the following code to your app:

app.ts

import { handleAuthRoutes } from '@logto/express';

app.use(handleAuthRoutes(config));

Implement sign-in and sign-out

With the routes registered, now let's implement the sign-in and sign-out buttons in the home page. We need to redirect the user to the sign-in or sign-out route when needed. To help with this, use withLogto to inject authentication status to req.user.

app.ts

import { withLogto } from '@logto/express';

app.get('/', withLogto(config), (req, res) => {
  res.setHeader('content-type', 'text/html');

  if (req.user.isAuthenticated) {
    res.end(`<div>Hello ${req.user.claims?.sub}, <a href="/logto/sign-out">Sign Out</a></div>`);
  } else {
    res.end('<div><a href="/logto/sign-in">Sign In</a></div>');
  }
});

Checkpoint: Test your application

Now, you can test your application:

1. Run your application, you will see the sign-in button.
2. Click the sign-in button, the SDK will init the sign-in process and redirect you to the Logto sign-in page.
3. After you signed in, you will be redirected back to your application and see the sign-out button.
4. Click the sign-out button to clear local storage and sign out.

Add Kakao connector

To add a social connector, go to the "Connector" tab in the Admin Console, then click on "Social connectors". From there, click "Add social connector".

In the openning modal, select "Kakao" and click "Next".

On the next page, you will see a two-column layout with the README content on the left and configuration on the right.

Feel free to follow the README file in place or read the following section to complete the configuration process. If you follow the in-place guide, you can skip the next section.

Set up Kakao login

Set up a project in the Kakao Devlopers Console

• Visit the Kakao Developers Console and sign in with your Kakao account.
• Click the Add an application to create new project or choose exist project.

Configure Kakao Login

Activate Kakao Login

• Click the Product Settings -> Kakao Login from the menu.
• Turn on Kakao Login Activation
• Add below URL into Redirect URI
  • http(s)://YOUR_URL/callback/${connector_id} (The connector_id can be found on the top bar of the Logto Admin Console connector details page.)
  • (Please replace YOUR_URL with your Logto URL, and choose http or https on your situation.)

Privacy Setting

• Click the Product Settings -> Kakao Login -> Consent Item from the menu.
• Change state of Nickname, Profile image, and Email to Required consent (You might not able to change Email to Required consent because of your project setting.)

Security Setting (Optional)

• Click the Product Settings -> Kakao Login -> Security from the menu.
• Click the Client secret code to generate secret code.
• Change Activation state to Enable. (If you enable it, secret code is necessary.)

Configure Logto

Config types

Name	Type
clientId	string
clientSecret	string?

clientId

clientId is REST API key of your project. (You can find it from summary of your project from Kakao developers console.)

clientSeceret

clientSecret is Secret Code of your project. (Please check Security Setting (Optional))

Save your configuration

Double check you have filled out necessary values in the Logto connector configuration area. Click "Save and Done" (or "Save changes") and the Kakao connector should be available now.

Enable Kakao connector in Sign-in Experience

Switch to the "Sign-in experience" tab, then click the "Sign-up and sign-in" tab.

note:

If it's the first time you enter the tab, you will see a quick introduction about Sign-in Experience and its basic configuration.

Select "None" for the "Sign-up identifier" to provide minimum sign-up effort for Kakao sign-in, which may increase your conversion rate.

In the "Social sign-in" section, add "Add Social Connector" and choose "Kakao". Then you should be able to see a button with text "Continue with Kakao" in the preview section.

Finally, click "Save changes" on the bottom right corner.

Testing and Validation

Return to your Express app. You should now be able to sign in with Kakao. Enjoy!

Further readings

Protect your API For native and single page apps, you'll need to call one or more API endpoints to retrieve and update data.
Learn more about identifying who's who and keeping your API secure.

User management We know you care about user management and activities, as we also do.
Learn more about how to know your users and see the figures like DAU and MAU graphically.

Localization From one regional business to a global corporate, the willingness to offer the best user experience won't change.
You can change current language phrases or add a new language without friction.

Customer IAM series Our serial blog posts about Customer (or Consumer) Identity and Access Management, from 101 to advanced topics and beyond.