Exploring App Responsiveness: ANR on Android vs. App Freezing on iOS

Raviraj Desai
3 min readAug 18, 2023

In the fast-paced world of mobile applications, user experience is paramount. App responsiveness, or the lack thereof, can greatly influence how users perceive and interact with an app. Two common issues that can hinder this responsiveness are ANR (Application Not Responding) on Android and App Freezing on iOS. In this blog post, we’ll delve into the nuances of these problems on both major mobile platforms and discuss their impact on users and developers.

ANR on Android: A Brief Overview

ANR, or Application Not Responding, is an issue that occurs on the Android platform when the UI thread, which is responsible for handling user interactions and UI updates, becomes unresponsive for a prolonged period. This can be triggered by long-running operations executed on the UI thread, such as network requests or complex computations. When an ANR occurs, Android displays a dialog to the user, informing them that the app has stopped responding and giving them the option to wait or close the app.

ANRs can have a negative impact on user experience, as unresponsive apps frustrate users and might lead them to uninstall the app altogether. From a developer’s perspective, diagnosing and fixing ANRs can be challenging due to their varied causes. Common solutions include moving time-consuming operations to background threads and optimizing UI code.

App Freezing on iOS: Understanding the Issue

In contrast, iOS apps can face a similar problem known as app freezing. App freezing occurs when an iOS app becomes unresponsive due to excessive CPU usage or blocking the main thread with time-consuming tasks. Unlike Android’s ANR, iOS doesn’t provide a distinct system-level dialog to users when an app freezes. Instead, users might notice the app’s interface becoming sluggish or completely frozen.

The consequences of app freezing on iOS are comparable to ANRs on Android. Users become frustrated when they can’t interact with the app smoothly, and this can lead to negative reviews and decreased user engagement. Developers addressing app freezing often need to identify and optimize performance bottlenecks, refactor code to offload heavy tasks from the main thread, and adopt techniques like asynchronous programming.

Mitigating Issues for a Seamless User Experience

To ensure a seamless user experience, developers on both platforms need to be vigilant about monitoring app responsiveness. Strategies include:

  1. Thorough Testing: Rigorous testing on various devices and scenarios can help uncover potential responsiveness issues early in the development process.
  2. Profiling Tools: Utilizing profiling tools provided by both platforms can assist in identifying performance bottlenecks and areas that need optimization.
  3. Background Processing: Offloading heavy tasks to background threads or queues can prevent the main thread from becoming overwhelmed.
  4. Asynchronous Programming: Employing asynchronous programming techniques can help keep the UI responsive while handling time-consuming operations.
  5. Regular Updates: Continuously optimizing app performance and responsiveness through updates demonstrates a commitment to user satisfaction.

In conclusion, app responsiveness is a critical factor in delivering a positive user experience. ANR on Android and app freezing on iOS are common issues that, when addressed with proper techniques, can contribute to smoother interactions and happier users. Developers who prioritize responsiveness are better poised to create successful and engaging mobile applications.

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Raviraj Desai

Assistant Vice President at Axis Bank (Android — Kotlin lover. Tech stack: MVVM, Dagger2, Coroutines, RxJava2 ,Flutter Enthusiast ,Ejabber