How to Get the Authentication ID of a User with a LOCAL Session in Firebase After Reloading the Site

Learn how to efficiently retrieve the `authentication ID` of a user with a `local session` in Firebase, even after a page reload. This guide simplifies the process and ensures smooth user experience.
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This video is based on the question https://stackoverflow.com/q/67355701/ asked by the user 'MoDi' ( https://stackoverflow.com/u/14977550/ ) and on the answer https://stackoverflow.com/a/67398837/ provided by the user 'shapkar' ( https://stackoverflow.com/u/13061503/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Retrieve the Authentication ID of a User with a LOCAL Session in Firebase After Reloading the Site

When developing applications with Firebase, you might encounter a common scenario: you want to retrieve a user's authentication ID after they have signed in and the page is reloaded. Particularly, if you are using a LOCAL session to store authentication data in the browser, this can pose a challenge if it’s not handled correctly.

In this guide, we’ll explore why you may find the user's authentication details undefined upon reloading the page and provide a simple solution to access this information through Firebase.

Understanding the Problem

After a user has successfully signed into your application using Firebase Authentication, their details are temporarily stored in the browser's local storage. However, upon reloading the page, you may attempt to access the data using:

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In this case, many developers notice that the output is undefined. This is because Firebase requires you to check the authentication state asynchronously after the page has loaded, rather than attempting to access the user details directly.

Solution: Subscribe to Authentication State Changes

To effectively manage and access user authentication data even after a page reload, you will need to utilize Firebase's built-in method to subscribe to authentication state changes. This ensures that your application responds to any changes in the user's sign-in status.

Step-by-Step Guide

Add Firebase SDK: Ensure that you have included the Firebase SDK in your project and initialized it properly.

Set Up Persistence: Before signing in, set the authentication persistence to LOCAL to maintain the user's session across page reloads.

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Sign in the User:

After setting up the persistence, sign in the user using their credentials.

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Subscribe to Auth State Changes:

Use the onAuthStateChanged method to listen for changes in the authentication state. This is where you can safely access the user object after the page reload.

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Retrieving user authentication details after page reloads can offer a seamless experience in your Firebase-based applications. By subscribing to authentication state changes, you can ensure that the authentication ID and other user details are readily accessible, even if the page is refreshed.

In summary, remember these key points:

Always set the authentication persistence before signing in.

Use onAuthStateChanged to handle changes in user authentication status.

Implementing these practices will greatly enhance your application's user experience, particularly in maintaining a smooth and persistent authentication state.

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