Resolving Cookies Not Working on Mobile While Testing Next.js Apps

Discover how to tackle the common issue of cookies not working on mobile devices when testing your Next.js application.
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Solving the Mystery of Non-Working Cookies in Your Next.js App on Mobile Devices

When working on web applications, particularly with frameworks like Next.js, developers often test their apps on different devices to ensure a smooth user experience. However, there can be frustrating scenarios that arise, such as cookies not functioning correctly on mobile devices. If you find yourself in a situation where your mobile testing yields no cookies being saved or sent back to your backend, you're not alone. In this post, we'll delve into why this issue can occur and how to resolve it effectively.

The Problem

You might have experienced this classic dilemma:

Your Next.js application works perfectly when accessed via localhost on your development machine.

But when you try to access it using a private IP address (e.g., 192.XXX.X.24:3000) from your mobile device, cookies fail to store and communicate effectively with your backend API.

This issue can be particularly troublesome since simulating mobile displays in development tools doesn’t provide the same insights into user experience as testing on a real device.

Understanding Cookies and SameSite Attribute

The root of the problem often lies in how cookies are configured when they are being sent from your server to the client. In web development, cookies have various attributes that dictate how they should be handled. One such attribute is SameSite.

The SameSite attribute can take potentially three values:

Strict: Cookies are not sent in requests originating from external sites.

Lax: Cookies are sent along with top-level navigations and will be sent along with GET requests initiated by third-party websites.

None: Cookies will be sent in all contexts, i.e., both in first-party and cross-origin contexts, but they must be Secure (sent over HTTPS).

The Issue at Hand

In your case, the cookies sent from your API were likely configured with SameSite: true. This configuration effectively treats the cookies as "SameSite" without explicitly defining a value, which defaults to Lax. As a result, when attempting to access your API via a private IP address, the cookies were blocked from being sent, leading to the problem you encountered.

Solution: Modify Cookie Attributes

Steps to Resolve the Cookie Issue

To ensure that cookies are sent correctly from your API to your mobile device when accessing your Next.js app, follow these steps:

Identify Your Cookie Settings:

Check how cookies are being set in your backend API. Look for any configurations related to SameSite.

Change SameSite to False:

Update your cookie configurations from SameSite: true to SameSite: false. This will allow the cookies to be sent alongside requests originating from your private IP address.

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Test Again:

Re-launch your Next.js app on your mobile device and try accessing it through your private IP. Confirm whether cookies are now being stored and sent back to your backend.

Conclusion

Testing a Next.js application on a mobile device can often lead you down unexpected paths, especially concerning cookies and user sessions. However, by understanding how cookie attributes like SameSite work and adjusting them accordingly, you can resolve issues related to cookies not functioning properly on mobile devices.

Armed with this information, you should be able to ensure a seamless development experience while also enhancing the overall user experience for mobile users. Happy coding!

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