Understanding and Resolving Third-Party Cookie Warnings in React Applications

As a React developer, you might occasionally encounter a console warning that says, “Third-party cookie will be blocked. Learn more in the Issues tab.” This can be particularly perplexing if the warning frequency increases with every second your application runs. Today, we’re going to delve into what causes this warning, why it’s important, and how you can resolve or mitigate it in your React projects.

What Triggers the Third-Party Cookie Warning?

The warning typically appears when your application tries to set or read a cookie in a context that the browser considers “third-party.” In many cases, this is due to cross-origin requests where the domain of the resource fetching or manipulating cookies does not match the domain of the resource being requested.

As web privacy increases, browsers like Google Chrome are phasing out support for third-party cookies, which are often used for tracking users across different sites. By the end of 2024, Chrome plans to block third-party cookies entirely. This initiative is part of a broader effort to enhance user privacy and security on the internet.

Strategies to Resolve the Warning

Here are a few strategies to address and possibly eliminate the third-party cookie warning in your React applications:

1. Adjust Cookie Settings

Adjust the attributes of your cookies to comply with new standards. Instead of setting cookies with SameSite=None; Secure for cross-site usage, opt for SameSite=Lax or SameSite=Strict. These settings ensure that cookies are sent only in a first-party context or in a more restricted cross-site context, respectively.

Example: Setting Cookie with JavaScript

document.cookie = "username=JohnDoe; SameSite=Lax; path=/; Secure";

2. Align Your Frontend and Backend Domains

To avoid the complications of cross-origin requests, host your frontend and backend on the same domain or subdomains of a common domain. This alignment makes all cookies first-party, which are less likely to be blocked by browsers.

Example: Hosting Configuration

• Frontend: https://app.example.com
• Backend: https://api.example.com

Ensure both are accessible through HTTPS to set cookies with the Secure attribute, which is required for SameSite=None.

3. Implement Alternative State Management Strategies

Consider using other mechanisms for maintaining session or state information between the client and the server. Local storage, session storage, or server-side sessions can sometimes replace cookies, especially when the data does not need to be sent to the server with every request.

Example: Using Local Storage in React

localStorage.setItem('sessionId', 'abc123');

Why It’s Important to Act Now

Handling these warnings proactively is crucial because once third-party cookies are phased out, any features depending on them will cease to function properly, potentially breaking your application or degrading the user experience. By adapting early, you can ensure a smoother transition as browser policies evolve.

Encountering third-party cookie warnings can be an opportunity to improve your application’s compliance with modern web standards and enhance user privacy. By adjusting cookie settings, aligning domain structures, and exploring alternative state management methods, you can mitigate or even eliminate these warnings, making your React application more robust and future-proof.