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There are two tools that you need to develop apps with Expo: a local development tool and a mobile client to open your app.
Local Development Tool: Expo CLI
Expo CLI is a tool for developing apps with Expo. In addition the command-line interface (CLI) it also has a graphical UI, Expo Developer Tools, that pops up in your web browser. With Expo Dev Tools you can quickly set up your test devices, view logs and more.
Expo Client helps view your projects while you're developing them. When you serve your project with Expo CLI, it generates a development URL that you can open in Expo Client to preview your app. On Android, Expo Client can also be used to view others' projects on expo.io. Expo Client works on devices, simulators, and emulators.
Required Android and iOS versions: The minimum Android version Expo supports is Android 4.4 and the minimum iOS version is iOS 9.0.
You don't need to manually install the Expo client on your emulator/simulator, because XDE will do that automatically. See the next sections of this guide.
Install Xcode through the Apple App Store. It'll take a while, go have a nap. Next, open up Xcode, go to preferences and click the Components tab, install a simulator from the list.
Once the simulator is open and you have a project open in XDE, you can press Open on iOS simulator in XDE and it will install the Expo Client to the simulator and open up your app inside of it.
Not working? Occasionally XDE will have trouble installing the Expo Client automatically, usually due to annoying small differences in your environment or Xcode toolchain. If you need to install the Expo Client on your simulator manually, you can follow these steps:
Extract the contents of the archive: mkdir Exponent-X.XX.X.app && tar xvf Exponent-X.XX.X.tar.gz -C Exponent-X.XX.X.app. You should get a directory like Exponent-X.XX.X.app.
Make sure Simulator is running.
At a terminal, run xcrun simctl install booted [path to Exponent-X.XX.X.app].
Download Genymotion (free version) and follow the Genymotion installation guide. Once you've installed Genymotion, create a virtual device - we recommend a Nexus 5, the Android version is up to you. Start up the virtual device when it's ready.
Once the emulator is open and you have a project open in XDE, you can press Open project in Expo on Android in XDE and it will install the Expo client to the emulator and open up your app inside of it. If you run into any issues follow our Genymotion guide.
To get started with Expo you don't necessarily need to have Node.js installed, but as soon as you start actually building something you'll want to have it. Download the latest version of Node.js.
Some macOS users encounter issues if they do not have this installed on their machine, so we recommend that you install Watchman. Watchman watches files and records when they change, then triggers actions in response to this, and it's used internally by React Native. Download and install Watchman.