How to build Slack sign-in with SvelteKit

For our new friends:

Logto is an Auth0 alternative designed for modern apps and SaaS products. It offers both Cloud and Open-source services to help you quickly launch your identity and management (IAM) system. Enjoy authentication, authorization, and multi-tenant management all in one.

We recommend starting with a free development tenant on Logto Cloud. This allows you to explore all the features easily.

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

Prerequisites

A running Logto instance. Check out the introduction page to get started.
Basic knowledge of SvelteKit.
A usable Slack account.

Create an application in Logto

Logto is based on OpenID Connect (OIDC) authentication and OAuth 2.0 authorization. It supports federated identity management across multiple applications, commonly called Single Sign-On (SSO).

To create your Traditional web application, simply follow these steps:

Open the Logto Console. In the "Get started" section, click the "View all" link to open the application frameworks list. Alternatively, you can navigate to Logto Console > Applications, and click the "Create application" button.
In the opening modal, click the "Traditional web" section or filter all the available "Traditional web" frameworks using the quick filter checkboxes on the left. Click the "SvelteKit" framework card to start creating your application.
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 SvelteKit with Logto

tip:

The following demonstration is built on SvelteKit 2.0.0.
The sample project is available in the GitHub repository.

Installation

Install Logto SDK via your favorite package manager:

npm
pnpm
yarn

npm i @logto/sveltekit

pnpm add @logto/sveltekit

yarn add @logto/sveltekit

Add Logto hook

In your hooks.server.ts file, add the following code to inject the Logto hook into your server:

hooks.server.ts
import { handleLogto } from '@logto/sveltekit';

export const handle = handleLogto(
  {
    endpoint: '<your-logto-endpoint>',
    appId: '<your-logto-app-id>',
    appSecret: '<your-logto-app-secret>',
  },
  {
    encryptionKey: '<a-random-string>',
  }
);

Since these information are sensitive, it's recommended to use environment variables:

hooks.server.ts
import { handleLogto } from '@logto/sveltekit';
import { env } from '$env/dynamic/private';

export const handle = handleLogto(
  {
    endpoint: env.LOGTO_ENDPOINT,
    appId: env.LOGTO_APP_ID,
    appSecret: env.LOGTO_APP_SECRET,
  },
  {
    encryptionKey: env.LOGTO_COOKIE_ENCRYPTION_KEY,
  }
);

If you have multiple hooks, you can use the sequence() helper function to chain them:

hooks.server.ts
import { sequence } from '@sveltejs/kit/hooks';

export const handle = sequence(handleLogto, handleOtherHook);

Now you can access the Logto client in the locals object. For TypeScript, you can add the type to app.d.ts:

import type { LogtoClient, UserInfoResponse } from '@logto/sveltekit';

declare global {
  namespace App {
    interface Locals {
      logtoClient: LogtoClient;
      user?: UserInfoResponse;
    }
  }
}

We'll discuss the user object later.

nota:

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

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:

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

This authentication process follows the OpenID Connect (OIDC) protocol, and Logto enforces strict security measures to protect user sign-in.
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.

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.

In the page where you want to implement sign-in and sign-out, define the following actions:

+page.server.ts
import type { Actions } from './$types';

export const actions: Actions = {
  signIn: async ({ locals }) => {
    await locals.logtoClient.signIn('http://localhost:3000/callback');
  },
  signOut: async ({ locals }) => {
    await locals.logtoClient.signOut('http://localhost:3000/');
  },
};

Then use these actions in your Svelte component:

+page.svelte
<form method="POST" action="?/{data.user ? 'signOut' : 'signIn'}">
  <button type="submit">Sign {data.user ? 'out' : 'in'}</button>
</form>

Checkpoint: Test your application

Now, you can test your application:

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

Add Slack connector

To enable quick sign-in and improve user conversion, connect with SvelteKit as an identity provider. The Logto social connector helps you establish this connection in minutes by allowing several parameter inputs.

To add a social connector, simply follow these steps:

Navigate to Console > Connectors > Social Connectors.
Click "Add social connector" and select "Slack".
Follow the README guide and complete required fields and customize settings.

nota:

If you are following the in-place Connector guide, you can skip the next section.

Set up Slack OAuth app

Set up Slack App

Go to the Slack API: Applications and sign in with your Slack account. If you don’t have an account, you can register for one.

Then, create an app.

Step 1: Find Client ID and Client Secret.

You can find the Client ID and Client Secret on the "Basic Information" section.

Step 2: Set up redirect URLs.

Go to the "OAuth & Permissions" section, you can find the "Redirect URLs" form.

In our case, this will be ${your_logto_endpoint}/callback/${connector_id}. e.g. https://foo.logto.app/callback/${connector_id}. The connector_id can be found on the top bar of the Logto Admin Console connector details page.

You can refer to the Slack API documentation for more details.

Configure your connector

In your Logto connector configuration, fill out the following fields with the values obtained from your App's "Keys and tokens" page's "OAuth 2.0 Client ID and Client Secret" section:

clientId: Your App's Client ID.
clientSecret: Your App's Client Secret.

scope is a space-delimited list of OpenID scopes. If not provided, the default scope is openid profile.

Config types

Name	Type
clientId	string
clientSecret	string
scope	string

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 Slack connector should be available now.

Once you create a social connector successfully, you can enable it as a "Continue with Slack" button in Sign-in Experience.

Navigate to Console > Sign-in experience > Sign-up and sign-in.
(Optional) Choose "Not applicable" for sign-up identifier if you need social login only.
Add configured Slack connector to the "Social sign-in" section.

Testing and Validation

Return to your SvelteKit app. You should now be able to sign in with Slack. Enjoy!

Create an application in Logto​

Integrate SvelteKit with Logto​

Installation​

Add Logto hook​

Implement sign-in and sign-out​

Regarding redirect-based sign-in​

Configure redirect URIs​

Checkpoint: Test your application​

Add Slack connector​

Set up Slack OAuth app​

Set up Slack App​

Configure your connector​

Config types​

Save your configuration​

Enable Slack connector in Sign-in Experience​

Testing and Validation​

Further readings​