[Fixed] Google Sign-In Not Working in Next.js with Firebase due to Cross-Origin-Opener-Policy Error – Firebase

The Problem:

Google Sign-In is not working in a Next.js application with Firebase due to the Cross-Origin-Opener-Policy error. When attempting to sign in, a popup window appears but fails to complete the sign-in process, resulting in the user not being properly signed in. The error message in the console indicates that the Cross-Origin-Opener-Policy policy is blocking the window.closed call. This issue occurs on Chrome but not on Firefox. Is the error a result of a misconfiguration of the Cross-Origin-Opener-Policy, and if so, how can it be correctly configured for Google Sign-in with Firebase in a Next.js application?

The Solutions:

Solution 1: Confirm Authorized Domains

Verify that the authorized domains or URIs are correctly configured in both Firebase and Google Cloud Platform (GCP) if you’re utilizing Google APIs. Ensure that your local development environment’s port (e.g., localhost:3000) is included in the authorized URIs.

Solution 2: Check Scope

Make sure that the scope requested during Google sign-in includes the necessary permissions. The profile and email scopes are typically required for user authentication.

Solution 2: Cross-Origin-Opener-Policy header

The error you’re encountering is caused by a mismatch between the Cross-Origin-Opener-Policy (COOP) headers of the parent page and the popup window. The COOP header controls whether a page can interact with a popup window that was opened by another page.

In this case, the error is likely occurring because the parent page and the popup window have different COOP headers. To fix this, you need to ensure that the COOP headers are the same for both pages.

You can set the COOP header in your Next.js application using the headers property in the next.config.js file. Here’s an example:

module.exports = {
  headers: {
    'Cross-Origin-Opener-Policy': 'same-origin'
  }
};

This will set the COOP header to same-origin, which will allow the parent page and the popup window to interact with each other.

Solution 3: Verify Environment Setup and Debug the Error

The Cross-Origin-Opener-Policy error you’re encountering is likely related to your development environment setup. Follow these steps to verify your environment and debug the error:

1. Confirm that you have followed the Next.js documentation for setting up your development environment. Refer to the Next.js Installation documentation for guidance.
2. Verify that you have correctly installed the Firebase SDK. You can check the Next.js Firebase documentation for detailed instructions.
3. Check the error logs in your developer tools (e.g., Chrome DevTools). Reproduce the issue and then inspect the network tab to observe any errors or warnings that may provide more context about the Cross-Origin-Opener-Policy violation.
4. Consider debugging your application at the point of authentication to pinpoint the exact source of the error. This can help identify any specific configuration issues or code errors that may be causing the problem.
5. If you’ve thoroughly followed the documentation and the solution doesn’t resolve the issue, provide more detailed information about the error, including the developer tools network logs, to receive further assistance.

Solution 4: Verify Firebase URL in Next.js Config

To resolve this issue, ensure that the Firebase URL is allowed in the Next.js configuration file. Add the following code snippet to the next.config.js file:

module.exports = {
  webpack: (config, { isServer }) => {
    if (!isServer) {
      config.resolve.fallback.fs = false;
    }

    return config;
  },
};

This change should allow seamless Google sign-in without encountering the Cross-Origin-Opener-Policy error.

Video Explanation: