Why Your React Native App’s Bundle Size Matters and How Expo Atlas Helps

Bundle size in React Native apps still affects startup time and memory footprint even with Hermes ahead-of-time compilation, and becomes critical for OTA updates, iOS App Clips, and Android Instant Apps. Expo Atlas is a bundle analysis tool that hooks into Metro's dependency graph to give a complete, module-by-module breakdown of what contributes to bundle size. Unlike Source Map Explorer, it resolves unmapped regions (up to 30% of bundle size) caused by Babel plugins. Setup in Expo projects is a single environment variable; vanilla React Native projects can use the `expo-atlas-without-expo` package to get the same functionality without adopting the full Expo framework.