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 Facebook sign-in experience (user authentication) with Python and  Logto.

Prerequisites

• A running Logto instance. Check out the introduction page to get started.
• Basic knowledge of Python.
• A usable Facebook 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 "Flask" 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 example uses Flask, but the concepts are the same for other frameworks.
• The Python sample project is available on our Python SDK repo.
• Logto SDK leverages coroutines, remember to use await when calling async functions.

Installation

Execute in the project root directory:

pip install logto # or `poetry add logto` or whatever you use

Init LogtoClient

First, create a Logto config:

client.py

from logto import LogtoClient, LogtoConfig

client = LogtoClient(
    LogtoConfig(
        endpoint="https://you-logto-endpoint.app",  # Replace with your Logto endpoint
        appId="replace-with-your-app-id",
        appSecret="replace-with-your-app-secret",
    ),
)

tip:

You can find and copy "App Secret" from application details page in Admin Console:

Also replace the default memory storage with a persistent storage, for example:

client.py

from logto import LogtoClient, LogtoConfig, Storage
from flask import session
from typing import Union

class SessionStorage(Storage):
    def get(self, key: str) -> Union[str, None]:
        return session.get(key, None)

    def set(self, key: str, value: Union[str, None]) -> None:
        session[key] = value

    def delete(self, key: str) -> None:
        session.pop(key, None)

client = LogtoClient(
    LogtoConfig(...),
    storage=SessionStorage(),
)

See Storage for more details.

Implement sign-in and sign-out

In your web application, add a route to properly handle the sign-in request from users. Let's use /sign-in as an example:

flask.py

@app.route("/sign-in")
async def sign_in():
  # Get the sign-in URL and redirect the user to it
  return redirect(await client.signIn(
      redirectUri="http://localhost:3000/callback",
  ))

Replace http://localhost:3000/callback with the callback URL you set in your Logto Console for this application.

If you want to show the sign-up page on the first screen, you can set interactionMode to signUp:

flask.py

@app.route("/sign-in")
async def sign_in():
  return redirect(await client.signIn(
      redirectUri="http://localhost:3000/callback",
      interactionMode="signUp", # Show the sign-up page on the first screen
  ))

Now, whenever your users visit http://localhost:3000/sign-in, it will start a new sign-in attempt and redirect the user to the Logto sign-in page.

Note Creating a sign-in route isn't the only way to start a sign-in attempt. You can always use the signIn method to get the sign-in URL and redirect the user to it.

After the user makes a signing-out request, Logto will clear all user authentication information in the session.

To clean up the Python session and Logto session, a sign-out route can be implemented as follows:

flask.py

@app.route("/sign-out")
async def sign_out():
  return redirect(
      # Redirect the user to the home page after a successful sign-out
      await client.signOut(postLogoutRedirectUri="http://localhost:3000/")
  )

Handle authentication status

In Logto SDK, we can use client.isAuthenticated() to check the authentication status, if the user is signed in, the value will be true, otherwise, the value will be false.

Here we also implement a simple home page for demonstration:

• If the user is not signed in, show a sign-in button;
• If the user is signed in, show a sign-out button.

@app.route("/")
async def home():
    if client.isAuthenticated() is False:
        return "Not authenticated <a href='/sign-in'>Sign in</a>"
    return "Authenticated <a href='/sign-out'>Sign out</a>"

Test your integration:

Open your Python app to test if the integration works. When you click the "Sign In" button, the page should be redirected to a Logto sign-in page, and you should be able to create a new account by entering username and password and complete the sign-in process.

Add Facebook 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 "Facebook" 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 Facebook login

Register a Facebook developer account

Register as a Facebook Developer if you don't have one.

Set up a Facebook app

1. Visit the Apps page.
2. Click your existing app or create a new one if needed.
   • The selected app type is up to you, but it should have the product Facebook Login.
3. On the app dashboard page, scroll to the "Add a product" section and click the "Set up" button on the "Facebook Login" card.
4. Skip the Facebook Login Quickstart page, and click the sidebar -> "Products" -> "Facebook Login" -> "Settings".
5. In the Facebook Login Settings page, fill ${your_logto_origin}/callback/${connector_id} in the "Valid OAuth Redirect URIs" field. The connector_id can be found on the top bar of the Logto Admin Console connector details page. E.g.:
   • https://your-logto-domain.com/callback/${connector_id} for production
   • https://localhost:3001/callback/${connector_id} for testing in the local environment
6. Click the "Save changes" button at the bottom right corner.
7. In the Facebook app dashboard page, click the sidebar -> "Settings" -> "Basic" and then you will get the App ID and App secret. The App ID is the clientId in your Logto connector conifg and the App secret is the clientSecret.

Test sign-in with Facebook's test users

You can use the accounts of the test, developer, and admin users to test sign-in with the related app under both development and live app modes.

You can also set the app to "live mode" by switching modes so that any Facebook user can sign in with the app.

• In the app dashboard page, click the sidebar -> "Roles" -> "Test Users".
• Click the "Create test users" button to create a testing user.
• Click the "Options" button of the existing test user, and you will see more operations, e.g., "Change name and password".

Publish Facebook sign-in settings

Usually, only the test, admin, and developer users can sign in with the related app under development mode.

To enable normal Facebook users sign-in with the app in the production environment, you may need to switch your Facebook app to live mode, depending on the app type. E.g., the pure business type app doesn't have the "live" switch button, but it won't block you from using it.

1. In the Facebook app dashboard page, click the sidebar -> "Settings" -> "Basic".
2. Fill out the "Privacy Policy URL" and "User data deletion" fields on the panel if required.
3. Click the "Save changes" button at the bottom right corner.
4. Click the "Live" switch button on the app top bar.

References

Config types

Name	Type
clientId	string
clientSecret	string

Facebook developer docs

• Facebook Login - Documentation - Facebook for Developers
• Manually Build a Login Flow
• Permissions Guide

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 Facebook connector should be available now.

Enable Facebook 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 Facebook sign-in, which may increase your conversion rate.

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

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

Testing and Validation

Return to your Python app. You should now be able to sign in with Facebook. 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.