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Viewing logs

Writing to the logs in an Expo app works just like in the browser: use console.log, console.warn and console.error. Note: we don't currently support console.table outside of remote debugging mode.

Recommended: View logs with Expo tools

When you open an app that is being served from Expo CLI, the app will send logs over to the server and make them conveniently available to you. This means that you don't need to even have your device connected to your computer to see the logs -- in fact, if someone opens the app from the other side of the world you can still see your app's logs from their device.

If you use our command line tool Expo CLI, bundler logs and app logs will both automatically stream as long as your project is running. To stop your project (and end the logs stream), terminate the process with ctrl+C.

While it's usually not necessary, if you want to see logs for everything happening on your device, even the logs from other apps and the OS itself, you can use one of the following approaches.

The following instructions apply to macOS.
  • brew install --HEAD libimobiledevice -g
  • Plug your phone in
  • idevicepair pair
  • Press accept on your device
  • Run idevicesyslog

  • In simulator, press ⌘ + /, or go to Debug -> Open System Log -- both of these open a log window that displays all of the logs from your device, including the logs from your Expo app.

  • Run instruments -s devices
  • Find the device / OS version that the simulator you are using, eg: iPhone 6s (9.2) [5083E2F9-29B4-421C-BDB5-893952F2B780]
  • The part in the brackets at the end is the device code, so you can now do this: tail -f ~/Library/Logs/CoreSimulator/DEVICE_CODE/system.log, eg: tail -f ~/Library/Logs/CoreSimulator/5083E2F9-29B4-421C-BDB5-893952F2B780/system.log

The following instructions apply to any OS that supports Android development.
  • Ensure Android SDK is installed
  • Ensure that USB debugging is enabled on your device (not necessary for emulator).
  • Run adb logcat