Expo

Documentation

Deploying to App Stores

This guide offers best practices around submitting your Expo app to the Apple iTunes Store and Google Play Store. To learn how to generate native binaries for submission, see Building Standalone Apps.
Although you can share your published project through the Expo client and on your expo.io profile, submitting a standalone app to the Apple and Google stores is necessary to have a dedicated piece of real estate on your users' devices. Submitting to these stores carries stronger requirements and quality standards than sharing a toy project with a few friends, because it makes your app available through a much wider distribution platform.
Disclaimer: Especially in the case of Apple, review guidelines and rules change all the time, and Apple's enforcement of various rules tends to be finicky and inconsistent. We can't guarantee that your particular project will be accepted by either platform, and you are ultimately responsible for your app's behavior. However, Expo apps are native apps and behave just like any other apps, so if you've created something awesome, you should have nothing to worry about!

It's a good idea to test your app on a device or simulator with a small screen (e.g. an iPhone SE) as well as a large screen (e.g. an iPhone X). Ensure your components render the way you expect, no buttons are blocked, and all text fields are accessible.
Try your app on tablets in addition to handsets. Even if you have ios.supportsTablet: false configured, your app will still render at phone resolution on iPads and must be usable.

  • Add a great icon. Icon requirements between iOS and Android differ and are fairly strict, so be sure and familiarize yourself with that guide.
  • Customize your primaryColor.
  • Make sure your app has a valid iOS Bundle Identifier and Android Package. Take care in choosing these, as you will not be able to change them later.

You'll use the app.json file to specify the version of your app, but there are a few different fields each with specific functionality.
  • version will apply both to iOS and Android. For iOS, this corresponds to CFBundleShortVersionString, and for Android this corresponds to versionName. This is your user-facing version string for both platforms.
  • android.versionCode functions as your internal Android version number. This will be used to distinguish different binaries of your app.
  • ios.buildNumber functions as your internal iOS version number, and corresponds to CFBundleVersion. This will be used to distinguish different binaries of your app.
To access these values at runtime, you can use the Expo Constants API:

  • Starting October 3, 2018, all new iOS apps and app updates will be required to have a privacy policy in order to pass the App Store Review Guidelines.
  • Additionally, a number of developers have reported warnings from Google if their app does not have a privacy policy, since by default all Expo apps contain code for requesting the Android Advertising ID. Though this code may not be executed depending on which Expo APIs you use, we still recommend that all apps on the Google Play Store include a privacy policy as well.

  • All apps in the iTunes Store must abide by the App Store Review Guidelines.
  • Apple will ask you whether your app uses the IDFA. Because Expo depends on Segment Analytics, the answer is yes, and you'll need to check a couple boxes on the Apple submission form. See Segment's Guide for which specific boxes to fill in.

  • Permissions are configured via the android.permissions key in your app.json file
  • By default, your app will include all permissions supported by Expo. This is so that your standalone app will match its behavior in the Expo Client and simply "work out of the box" no matter what permissions you ask for, with hardly any configuration needed on your part.
  • There are some drawbacks to this. For example, let's say your To-do list app requests CAMERA permission upon installation. Your users may be wary of installing since nothing in the app seems to use the camera, so why would it need that permission?
  • To remedy this, simply add the android.permissions key in your app.json file, and specify which permissions your app will use. A list of all Android permissions and configuration options can be found here.
  • To use only the minimum necessary permissions that Expo requires to run, set "permissions" : []. To use those in addition to CAMERA permission, for example, you'd set "permissions" : ["CAMERA"].

  • It's helpful to glance over Common App Rejections.
  • Binaries can get rejected for having poorly formatted icons, so double check the App Icon guide.
  • Apple can reject your app if elements don't render properly on an iPad, even if your app doesn't target the iPad form factor. Be sure and test your app on an iPad (or iPad simulator).
  • Occasionally people get a message from Apple which mentions an IPv6 network. Typically this is just Apple's way of informing you what kind of network they tested on, and the actual "IPv6" detail is a red herring. All of Expo's iOS code uses NSURLSession, which is IPv6-compatible. More info.

If your app asks for system permissions from the user, e.g. to use the device's camera, or access photos, Apple requires an explanation for how your app makes use of that data. Expo will automatically provide a boilerplate reason for you, such as "Allow cool-app to access the camera", however these must be customized and tailored to your specific use case in order for your app to be accepted by the App Store. To do this, override these values using the ios.infoPlist key in app.json, for example:
"infoPlist": {
  "NSCameraUsageDescription": "This app uses the camera to scan barcodes on event tickets."
},
The full list of keys Expo provides by default can be seen here. Unlike with Android, on iOS it is not possible to filter the list of permissions an app may request at a native level. This means that by default, your app will ship with all of these default boilerplate strings embedded in the binary. You can provide any overrides you want in the infoPlist configuration. Because these strings are configured at the native level, they will only be published when you build a new binary with expo build.

If your app uses a language besides English, you can optionally provide localized strings for the system dialogs. For example, in app.json, you can provide
"locales": {
  "ru": "./languages/russian.json"
}
...where russian.json looks like:
{
  "NSContactsUsageDescription": "Hello Russian words"
}