Safari IOS Freeze: React, Firebase, And Web Inspector Mystery

Have you ever encountered a frustrating issue where your website works perfectly fine in development but mysteriously freezes or gets stuck in an infinite reload loop on Safari iOS? This is precisely the problem many developers are facing, particularly when using React, Firebase, and localStorage. Let's dive into this intriguing issue and explore potential solutions.

The Curious Case of the Frozen Safari iOS

Many developers have reported a peculiar problem on iPhone's Safari and Chrome browsers (which also uses WebKit). The ProductPage and sometimes the Shop page of their websites freeze or get caught in a constant reload loop. Here's what happens:

• The page begins reloading repeatedly.
• The layout partially renders and then freezes.
• Sometimes, the screen remains blank.

However, the most baffling part is that the moment the iPhone is connected to a Mac and the Web Inspector is opened, the bug vanishes entirely! This behavior is consistently reproducible only on Safari iOS and Chrome iOS.

Steps to Reproduce the Issue

To better understand the problem, let's outline the steps to reproduce it:

1. Open Safari on your iPhone (in normal mode, not private).
2. Navigate to a website experiencing this issue, for example, https://muttergames.com/shop.
3. Open any product page.
4. Observe that after a second or two, the page freezes or reloads infinitely.
5. Connect your iPhone to your Mac via USB.
6. Open Safari's Develop menu and select your iPhone, then open Web Inspector.
7. Refresh the same page.

Notice that the problem disappears as soon as the Web Inspector is active. This makes debugging incredibly challenging and points towards a deeper, more elusive cause.

Expected Behavior

Ideally, the page should load normally on Safari iOS without requiring the remote Web Inspector to be open. This is the expected behavior on desktop browsers and other mobile browsers, making the Safari iOS issue particularly frustrating.

Environment Details

To further narrow down the issue, it's essential to consider the environment in which it occurs:

• Device: iPhone (specific model varies, but the issue is prevalent across different models).
• iOS Version: 17.x (and potentially earlier versions).
• Browsers:
  • Safari iOS (latest).
  • Chrome iOS (latest).
• Notably, the issue does NOT occur in:
  • Desktop Safari.
  • Desktop Chrome.
  • Private mode Safari iOS.
  • Android browsers.

The fact that the issue is isolated to Safari and Chrome on iOS suggests a WebKit-specific problem or an interaction between WebKit and the libraries being used.

Project Tech Stack: A Closer Look

Understanding the technology stack of the affected projects can provide clues about potential causes. Here's a common stack where this issue has been observed:

Frontend

• React + Vite: A popular combination for building modern web applications.
• Firebase Auth: Used for user authentication, often with anonymous and email/password options.
• Firestore Real-time Listeners: Employed for synchronizing data, such as shopping carts.
• localStorage: Utilized for storing cart and shipping information.
• No Service Worker Active: This eliminates service workers as a potential cause.

Backend

• Firebase Admin API: Used for backend operations and data management.

Potential Causes and Insights

Several factors might contribute to this perplexing behavior. Let's explore some potential causes and insights:

Race Conditions, WebKit Scheduling Bugs, or React Effect Timing Issues

The fact that the issue disappears when devtools are open strongly indicates a race condition, a WebKit scheduling bug, or a React effect timing issue. Opening Web Inspector can alter the timing and execution order of JavaScript code, potentially masking the underlying problem.

Triggers Around Authentication and Cart Loading

The issue might be triggered around specific events or operations, such as:

• onAuthStateChanged + signInAnonymously(): Firebase authentication events.
• Cart loading logic + localStorage updates: Operations involving local storage.
• Multiple useEffect triggers running before layout stabilization: React's effect hooks running in an unpredictable order.

These events often involve asynchronous operations and state updates, which can be susceptible to race conditions and timing issues.

Additional Notes and Observations

Several additional observations can help in diagnosing the problem:

• Clearing Safari's cache and website data does NOT fix the issue.
• The issue occurs ~70–90% of the time on the ProductPage when not debugging, making it highly reproducible.
• The problem completely disappears once devtools are open, reinforcing the timing-related nature of the bug.

Digging Deeper: Potential Solutions and Workarounds

Given the complexities of the issue, there's no one-size-fits-all solution. However, here are several strategies to explore:

1. Investigate React Effect Dependencies and Timing

• Carefully review your useEffect hooks: Ensure that dependencies are correctly specified and that effects are not triggered unnecessarily or in the wrong order.
• Consider using useLayoutEffect: If you're performing DOM manipulations, useLayoutEffect might be more appropriate as it runs synchronously after the DOM is updated but before the browser has a chance to paint.
• Debounce or throttle updates: If you're updating state frequently, consider debouncing or throttling the updates to avoid overwhelming the browser.

2. Optimize Firebase Authentication and Data Loading

• Minimize authentication calls: Reduce the frequency of authentication calls, especially anonymous sign-ins, if possible.
• Optimize Firestore listeners: Ensure that your Firestore listeners are efficient and only fetching the necessary data.
• Implement loading states: Use loading states to prevent UI updates until data is fully loaded, reducing the chance of race conditions.

3. Review localStorage Usage

• Minimize localStorage operations: Reduce the number of reads and writes to localStorage, as these can be synchronous and potentially block the main thread.
• Consider asynchronous storage: Explore alternative asynchronous storage options if localStorage is causing performance issues.

4. Debug with Web Inspector and Timers

• Use console.log statements strategically: Add console.log statements to track the execution order of your code, especially within useEffect hooks and asynchronous operations.
• Utilize setTimeout for debugging: Introduce small delays using setTimeout to simulate different timing scenarios and identify potential race conditions.

5. Check for WebKit Bugs and Updates

• Stay updated with WebKit releases: Keep an eye on WebKit release notes and bug reports for any known issues that might be related to your problem.
• Report your findings: If you suspect a WebKit bug, consider reporting it to Apple so they can investigate and address the issue.

Has Anyone Seen This Before? A Community Call for Insights

This Safari iOS freezing issue is a complex and persistent problem that requires a collaborative effort to solve. Many developers have encountered similar behavior when using React, Firebase, and localStorage. Sharing experiences and insights can significantly accelerate the discovery of solutions.

If you've seen similar issues on Safari iOS where React, Firebase, and localStorage lead to UI freezes unless Web Inspector is active, your insights would be greatly appreciated. Known WebKit bugs or specific patterns you've observed can provide valuable clues.

Conclusion: Unraveling the Safari iOS Mystery

The Safari iOS freezing issue is a challenging problem that highlights the complexities of web development, especially when dealing with asynchronous operations, state management, and browser-specific behaviors. By understanding the potential causes, exploring various solutions, and collaborating with the community, we can work towards unraveling this mystery and ensuring a smooth user experience on Safari iOS.

For more information on debugging WebKit, you might find this resource helpful: WebKit Debugging Guide