There are many reasons why an app might be slow. It could be due to a slow network, a slow backend, or a slow client. It could also be due to a memory leak, unnecessary re-renders, or large bundle sizes.
Here are some tips to help you investigate and fix performance issues:
Use the React DevTools Profiler
The React DevTools Profiler helps you visualize how components render and identify costly renderings. It can also help you identify unnecessary re-renders.
Check for Unnecessary Renders
Ensure that components don’t render more often than needed. Be clear about the useEffect dependencies and avoid creating new objects or arrays every render, as these can trigger unnecessary child component renders. Tools like why-did-you-render can help spot unnecessary re-renders.
Analyze Bundle Size
Use your production build to analyze your bundle size. Tools like webpack-bundle-analyzer or source-map-explorer can help you see if large libraries or unused code is slowing down the initial load.
Optimize Images & Assets
Ensure images are appropriately sized and use modern formats. Also, consider using CDNs for assets that don’t change often.
Lazy Load Components
Use lazy() and dynamic imports to split your bundle and load components only when they’re needed. This can help reduce the initial load time.
Check Network Requests
Slow API calls or fetching large amounts of data can affect performance. Optimize your backend, paginate data, or cache results. You can also use tools like @tanstack/react-query or swr to help manage data fetching and caching.
Use Production Build for Testing
Ensure you’re testing the performance on a production build, as development builds are often slower due to extra checks and logs.
Regularly profiling and monitoring your app can help you spot and fix performance issues before they become significant problems. You can use tools like Lighthouse or Calibre to monitor your app’s performance over time.