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# Measure and improve performance

Below is a video of a React Native EU talk where we see how to

- use Flashlight to measure the startup performance of a dummy app with lots of performance issues
- use different analysis tools to debunk the issues and fix them:
  - React DevTools
  - JS Hermes Flame graph
  - Android Studio

The code of the app is available [here](https://github.com/Almouro/test-app-performance-issues).

:::tip
The video uses an old version of Flashlight which required you to write a TS file. Now, you only have to run this command below 🥳:

```bash
flashlight test --bundleId com.reactnativefeed \
  --testCommand "adb shell am start com.reactnativefeed/.MainActivity" \
  --duration 15000
```

:::

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