Optimize React Native Flatlist: ProCoders’ Performance Hacks in Several Steps

React Native is a popular framework to build mobile apps for both iOS and Android using JavaScript and React.

The best part? You can write one codebase and have it work across platforms, huge time saver. Many companies including some we have worked with here at ProCoders choose React Native because it offers a native like experience without needing to develop separate apps for different platforms.

While React Native is great for efficiency, like any technology it needs to be optimized for the best performance. If not, apps can feel slow, consume too much memory or drain a device’s battery faster than users would like.

That’s where optimization becomes critical—it’s the difference between a smooth responsive app and one that frustrates users. At ProCoders we have helped many clients fine tune their React Native apps and in this article we will share some of the optimization hacks we’ve learned along the way.

React Native General Performance Optimization

Avoid Inline Functions

Inline functions in JSX might seem convenient but they can cause performance issues by triggering unnecessary re-renders. Every time a component re-renders the inline function within the render function is re-created which React interprets as a change and triggers more render cycles than necessary.

ProCoders Hack: To avoid this you can use the useCallback() hook for functional components or bind functions in the constructor for class components. This ensures functions are only re-created when absolutely necessary and optimizes the render process and performance.

Optimize Render Cycles

Unnecessary re-renders are one of the biggest culprits of performance lags in React Native apps. Using React.memo for functional components or shouldComponentUpdate for class components can help control when a component re-renders by checking if its props have changed. Optimizing render cycles can significantly improve flatlist performance.

ProCoders Hack: For components that rely on complex data structures you can implement custom comparison logic for deep comparisons. This gives you more control over when re-renders should happen and avoid performance hits.

React Native Image Optimization Tips: Cached Optimized Images

Lazy Loading Images

Loading all images at once can increase memory usage and slow down your app’s performance. Instead, you should lazy load images—only load them when they are visible on the screen. This reduces memory consumption and speeds up the initial load time.

ProCoders Hack: The react-native-fast-image library is a great tool for this, it has efficient caching and loading mechanisms that further improves performance when dealing with images.

Use Proper Image Formats

Choosing the right image format can make a big difference in load times. For example using WebP images which are smaller in size without losing quality can reduce load times and save memory.

ProCoders Hack: To make sure your images are optimized use libraries like react-native-image-resizer to resize and compress images, reducing their size without sacrificing clarity or performance.

React Native Optimization Hacks: Large Lists

FlatList Performance Optimization

When dealing with large datasets rendering everything at once can cause significant performance bottlenecks. Instead of using ScrollView which renders all items at once, use FlatList which lazily renders items as needed, improves memory usage and performance. Setting the initialNumToRender can give a big performance boost by defining a precise number of items to render initially.

The maxToRenderPerBatch prop controls the number of items rendered in each batch during scrolling, balances visual presentation and JavaScript execution performance. Adjusting the updateCellsBatchingPeriod allows for less frequent batch renders which can optimize rendering process. Using maxToRenderPerBatch along with less frequent batches can help manage the number of items rendered at a time and reduce potential blank areas. Increasing the number of items rendered per batch can reduce visual blank areas and enhance the visual appeal.

But using the removeClippedSubviews prop can cause choppy scroll animations on not so good devices due to increased computational demands. React Native’s implementation of FlatList built upon the VirtualizedList component addresses various performance aspects including memory consumption and responsiveness. The keyExtractor prop is required for caching and as a React key to track item re-ordering, ensures smooth performance when items in the list are re-ordered. Increasing the number of items rendered per batch can also reduce visual blank areas during scrolling and improve the visual experience.

ProCoders Hack: To further boost performance enable removeClippedSubviews, initialNumToRender and maxToRenderPerBatch in FlatList. These options allows you to control how many items are rendered initially and how off-screen items are handled, reduces memory consumption.

Virtualization of Lists

For very large lists virtualization is key to performance. FlatList and SectionList has props like windowSize and getItemLayout that gives you more control over how lists are rendered, so only the items currently in view are rendered and others are kept in memory efficiently. The windowSize affects the chances of encountering blank space while scrolling, the larger the windowSize the less chances of blank space. The default value for windowSize is 21, so you can understand its impact on performance and memory consumption.

Using getItemLayout is a desirable optimization technique that eliminates the need of dynamic calculations of item sizes. Using light components can further improve rendering speed by reducing the weight of images and effects. getItemLayout also helps in managing async layout calculations, improves performance when list items have uniform height. windowSize is a measurement unit representing a proportion of the viewport height, affects rendering and memory usage. Adjusting the number passed to windowSize can balance visual smoothness and resource usage. Overall using getItemLayout is a very desirable optimization technique for React Native applications.

ProCoders Hack: When rendering long lists it’s helpful to use placeholders (also known as skeleton screens) to provide visual feedback to users while the actual data loads. By showing a simplified placeholder version of the list items you keep the user engaged and avoid perceived lags. Libraries like react-native-skeleton-placeholder can help you implement this, creates a smoother experience especially for slow network connections.

React Native Apps Performance by Reducing App Size for a Big Performance Boost

Code Splitting and Bundle Optimization

Code splitting is a smart way to keep your app’s initial load time low by only loading the code necessary for the current screen. Using dynamic imports and code splitting techniques ensures your app remains lightweight and fast even as it grows in complexity.

ProCoders Hack: Use react-native-bundle-visualizer to analyze your bundle size and identify unnecessary or bulky modules. This tool helps you reduce your JavaScript bundle size which directly impacts the app’s performance.

Minimize Third-Party Libraries

Third-party libraries can add weight to your app, increases both bundle size and load times. Be selective about which libraries you include and remove unused dependencies to keep your app lean.

ProCoders Hack: Whenever possible opt for lightweight alternatives or implement custom solutions tailored to your app’s needs. This reduces the app size and improves maintainability and performance.

React Native Apps Performance by Reducing App Size for a Big Performance Boost

Code Splitting and Bundle Optimization

Code splitting is a smart way to keep your app’s initial load time low by only loading the code necessary for the current screen. Using dynamic imports and code splitting techniques ensures your app remains lightweight and fast even as it grows in complexity.

ProCoders Hack: Use react-native-bundle-visualizer to analyze your bundle size and identify unnecessary or bulky modules. This tool helps you reduce your JavaScript bundle size which directly impacts the app’s performance.

Minimize Third-Party Libraries

Third-party libraries can add weight to your app, increases both bundle size and load times. Be selective about which libraries you include and remove unused dependencies to keep your app lean.

ProCoders Hack: Whenever possible opt for lightweight alternatives or implement custom solutions tailored to your app’s needs. This reduces the app size and improves maintainability and performance.

From React to Node.js, ProCoders doesn’t just code—we optimize with expert hacks for 50+ languages and frameworks.

React Native Performance Improvement: Memory Management

Avoid Memory Leaks

Memory leaks can slow down your app over time as unmounted components hold onto resources like event listeners or references. This often happens when components are not cleaned up properly after being removed from the DOM.

ProCoders Hack: To avoid this always use cleanup functions in hooks like useEffect or component lifecycle methods like componentWillUnmount. These cleanups remove any event listeners, subscriptions or side effects when components unmount, prevents memory bloat.

Clear Unnecessary State

Efficient state management is key to memory usage. Holding onto unnecessary state can cause memory bloat which impacts the app’s performance.

ProCoders Hack: For complex state management consider using useReducer instead of useState. This helps manage state updates more efficiently, so you don’t end up with redundant re-renders or stale data in memory.

How to Optimize React Native Apps: Optimize Animations

Use Native Driver for Animations

Smooth animations are important for good user experience, but animations can be resource intensive. React Native has the useNativeDriver option which pushes animation calculations to the native side, so animations are smoother and more fluid without bogging down the JavaScript thread.

ProCoders Hack: For more complex animations consider using the react-native-reanimated library. It’s optimized for performance and gives you more flexibility to deliver high quality animations that don’t hurt performance.

Minimize Re-renders during Animations

Animations should run without interruption, but re-renders during animations can cause frame drops which leads to choppy or inconsistent animations.

ProCoders Hack: Use InteractionManager.runAfterInteractions to delay any non-critical renders or actions until after the animations are complete. This keeps the animation smooth and doesn’t interfere with performance.

React Native App Optimization Tips: Efficient State Management

Use Context API or Redux Wisely

State management is key to prevent redundant re-renders. When using Context API or Redux, limit the number of components that subscribe to state changes. Too many subscriptions can cause excessive re-renders and performance issues.

ProCoders Hack: In Redux use selectors and only connect components that really need access to the global store. This reduces the number of components that re-render whenever the state changes and makes the app more efficient.

Don’t Overuse Context

While Context API is a powerful tool for state management, overusing it can lead to performance degradation especially when large component trees are re-rendered unnecessarily.

ProCoders Hack: Use React.memo and useContext selectively. Memoization helps you control which components should re-render and prevent unnecessary updates in your app.

React Network Request Optimization

Cache Network Requests

Frequent network requests can slow down your app and consume both performance and data. Caching API responses when possible can significantly improve performance especially for static or rarely changing data.

ProCoders Hack: Libraries like react-query or axios-cache-adapter are great for caching requests, so repeated network calls are avoided and previously fetched data is available without delay.

Debounce Input

Input fields like search bars can cause performance issues if they trigger too many API requests while the user is typing. To prevent this debounce input and delay the request until the user stops typing reducing the load on the network and the app.

ProCoders Hack: You can debounce easily with lodash.debounce or create custom hooks that delay actions, optimizing performance and improving the user experience.

ProCoders React Native Tips: Use Proguard for Android

Minify Code for Android

Proguard is a tool that minimizes and shrinks Android app code by removing unused code and resources, making the app lighter and more efficient. Enable Proguard in your Android build process and the bytecode will be minimized and the app will load faster and perform better.

ProCoders Hack: Customize Proguard rules to control how code is minified without breaking functionality. This way you have full control over your app’s performance while still having the benefits of minified code.

React Native Performance Tunning: Navigation

Use react-navigation Correctly

react-navigation is used to manage app navigation but if not optimized can cause unnecessary re-renders and slow transitions.

ProCoders Hack: To improve navigation performance use React.memo to memoize navigation screens and prevent redundant re-renders. Also enable lazy in react-navigation to load screens only when needed, reducing initial load times and overall app performance.

ProCoders’ Experience to Improve React Native Performance

For Roth River’s IoT development we used React to build a cross-platform mobile app that connected whiskey lovers and distillers in a whole new way. With React Native we built a single codebase that worked perfectly on both iOS and Android, saving time and making the app feel native to each platform.

Optimizing the app was key. We focused on things like efficient state management and smart image handling to ensure real-time updates flowed smoothly, giving users the experience they expected – whether tracking their whiskey’s aging process or making custom requests. Thanks to these optimizations the app runs fast and feels responsive, bringing Roth River’s vision to life and allowing us to deliver a polished product faster than expected.

React Performance Tips: Conclusion

optimizing your React Native app is crucial to have a smooth user experience and good performance. By applying these hacks like minimizing re-renders, optimizing images, manage state wisely and reduce memory consumption you can significantly improve your app’s speed and responsiveness.

At ProCoders we have seen how these strategies can turn a slow app into a high-performance product. With the right approach you can unlock the full potential of React, deliver an app that both users and developers will love. Ready to optimize your app? Let ProCoders help you achieve top performance!