Build Standalone Expo .apk and .ipa with Turtle CLI

February 05, 2021 - 16 min

This article was updated on February 05, 2021.

A great way to start writing React Native applications is to use Expo. You don’t even need to setup a development environment to get started thanks to Snack, an online React Native application editor. Your application is public by default. Sharing has never been that easy.

Photo by Wexor Tmg on Unsplash Brown turtle swimming underwater, Photo by Wexor Tmg on Unsplash

However, you would like to share an application exclusively with some people, not through an app store or any public channel. One possibility is to share the built application file, e.g. an .apk file for Android and an .ipa file for iOS.

Expo is so great a service (oh, and did I mention free?) that they offer you to publish your app on their servers and if you wanted to build these .apk and .ipa files, you could do so on their servers.

The flow looks like:

$ expo publish
$ expo build:<PLATFORM>

and you obtain a nice URL to the artifact created for you when the build finishes.

But, again, this is public. On a server you don’t control. (Although, if you made the same mistake as I did, a ticket to their support can delete any files you had wished to keep private. 🥇)

Luckily for you, Expo provide the tools they are using on their servers for free (did I mention they’re great!?). The build process relies on a CLI tool called turtle-cli. It is open-source and available on GitHub.

Let us go through an example of how to create your application file without resorting to Expo servers. That means you can keep an application private and also build your application while being offline.

The following instructions assume you have bash and Node.js available. In my experience, using the current LTS version of Node.js (version 14.15.4) works best.

Caveat: I could not complete the iOS instructions to the end since I do not have an Apple Developer paid account.

We will go through the following steps:

1. Turtle CLI
2. Create a dummy application
3. Publish Expo app on local server
4. Create APK file — Android
5. Create IPA file — iOS
6. Distribute and install
- 6.1. on Android
- 6.2. on iOS
Resources

A condensed version of these steps without much explanation or context is available on the accompanying GitHub repository.

1. Turtle CLI

To install Turtle CLI, run

$ npm install -g turtle-cli

This will make command turtle globally available on your system. To verify it was correctly installed, let’s print the version:

$ turtle -V
0.20.7

2. Create a dummy application

Let’s create a dummy application using Expo CLI. In your terminal, run

$ npx expo init ExampleApplication

It will ask you a few questions:

# Expo version 4.1.6
? Choose a template: › - Use arrow-keys. Return to submit.
    ----- Managed workflow -----
❯   blank                 a minimal app as clean as an empty canvas
    blank (TypeScript)    same as blank but with TypeScript configuration
    tabs (TypeScript)     several example screens and tabs using react-navigation and TypeScript
    ----- Bare workflow -----
    minimal               bare and minimal, just the essentials to get you started
    minimal (TypeScript)  same as minimal but with TypeScript configuration

The blank template is enough for us.

If you have yarn installed, Expo will use it by default to install dependencies. You can use the --npm flag in the init command if you’d prefer to use npm instead.

Once it’s done setting up your project, you should see the following output in the terminal:

Your project is ready at ./ExampleApplication
To get started, you can type:

  cd ExampleApplication
  yarn start

Let’s verify the generated boilerplate works:

To finish setting up the dummy application, you need to configure the app.json file because some configuration keys must be specified to build a standalone app.

If you would like to know more about these standalone app specific configurations, check Expo’s documentation for iOS and for Android.

For this tutorial, it is only necessary to specify the keys "bundleIdentifier" under "ios", and "package" under "android" in your app.json file:

...
    "ios": {
      ...
      "bundleIdentifier": "com.example.exampleApplication",
      ...
    },
    "android": {
      ...
      "package": "com.example.example_application",
      ...
    }
...

3. Publish Expo app on local server

Expo has this notion of app publishing: it allows you to share a link or QR code to Expo’s website and anyone can run your app through the Expo app on their devices.

Having your app published is also necessary for over-the-air (OTA) updates, allowing seamless updates to your application, and to publish your application (i.e. building your application files on Expo servers).

You would typically run

$ expo login -u $EXPO_USERNAME -p $EXPO_PASSWORD
$ expo publish

and your app would then be available at https://expo.io/<EXPOUSERNAME>/<APPNAME>.

To have your Expo app “published” on your local server (and avoid public publishing on Expo servers), you will use a different command:

$ expo export --dev --public-url <your-url-here>

The --dev flag is necessary because you will use a non-https server to publish your Expo app. Note that this prevents you from using OTA updates.

Your server does not need to be running for this step, but you do need to know which local URL you are going to use in advance. This tuorial assumes you will run a local server at http://127.0.0.1:8000.

You can now export the app:

$ expo export --dev --public-url http://127.0.0.1:8000
...
Export was successful. Your exported files can be found in dist

This command will create a dist directory containing the iOS and Android JavaScript bundles and the different assets you are using.

dist
├── android-index.json
├── assets
│   ├── 13685372945d816a2b474fc082fd9aaa
│   ├── 140c53a7643ea949007aa9a282153849
│   ├── ...
│   ├── fdbedb7e67aa7c0ecad83d9c2fa4dfba
│   └── fdc01171a7a7ea76b187afcd162dee7d
├── bundles
│   ├── android-a9defc54fb2ffdb7e6fdaf5b8d0be751.js
│   └── ios-a29c3e4ac97a2abdc5208fd4f06e7708.js
└── ios-index.json

You can now serve the dist directory on your web server, e.g.

$ npx http-server -p 8000 dist

Note: if for some reason you need to re-export your application (because you modified your app.json file since the last export, for instance), you must first remove the dist directory:

# assuming you are at the root of the project
$ rm -rf dist
$ expo export --dev --public-url http://127.0.0.1:8000

4. Create APK file — Android

First, verify that your local server is running. For example, you should see a similar output:

$ curl http://127.0.0.1:8000/android-index.json
{"name":"ExampleApplication","slug":"ExampleApplication","version":"1.0.0","orientation":"portrait","icon":"./assets/icon.png","splash":{"image":"./assets/splash.png","resizeMode":"contain","backgroundColor":"#ffffff","imageUrl":"http://127.0.0.1:8000/assets/201a91bd1740bb1d6a1dbad049310724"}...

4.1. Prerequisites

For Turtle CLI to work correctly to create an .apk file for Android, you need to make sure the following dependency is installed: Java Development Kit (version 8).

If you know which Expo SDK version you are going to use, you can run

$ turtle setup:android --sdk-version <SDK-VERSION>

This will take some time:

$ turtle setup:android --sdk-version 40.0.1
Feb 4 08:20:37 turtle[48488] INFO:  Downloading Android SDK
  platform: "android"
  buildPhase: "setting up environment"
downloading [====================] 98% 0.5s
...
Feb 4 08:30:03 turtle[48488] INFO:  shell app for SDK 40.0.1 doesn't exist, downloading...
  platform: "android"
  buildPhase: "setting up environment"
downloading [=================== ] 94% 1.1s
Feb 4 08:30:23 turtle[48488] INFO:  shell app has been downloaded
  platform: "android"
  buildPhase: "setting up environment"
...
Feb 4 08:31:58 turtle[48488] INFO:  dependencies installed!
  platform: "android"
  buildPhase: "setting up environment"
Feb 4 08:31:58 turtle[48488] INFO:  it's all set!
  platform: "android"
  buildPhase: "setting up environment"

In the meantime, you can move on to the next section.

4.2. Create Keystore

Just like any other Android app, this app must be signed with some security certificates. In Android-land, as far as I understand, it’s called a keystore. The instructions to create such a keystore file are available on the Android Developers documentation.

Basically, just create a dummy Android project with Android Studio, and then go to Build > Generate Signed Bundle / APK.... Choose APK and press Next. The UI will ask you which app you want to sign, and your dummy app should be pre-selected. On the same screen, press on the button Create new...; just fill the form and you’re good to go.

Alternatively, if you have keytool CLI utility available on your system (you can check that by trying keytool --help in your terminal), you can generate a keystore file with the following command

$ keytool -genkeypair -v -keystore keystore.jks -alias keyalias -keyalg RSA -keysize 2048 -validity 9125
Enter keystore password:
Re-enter new password:
What is your first and last name?
  [Unknown]:
What is the name of your organizational unit?
  [Unknown]:
What is the name of your organization?
  [Unknown]:
What is the name of your City or Locality?
  [Unknown]:
What is the name of your State or Province?
  [Unknown]:
What is the two-letter country code for this unit?
  [Unknown]:
Is CN=Unknown, OU=Unknown, O=Unknown, L=Unknown, ST=Unknown, C=Unknown correct?
  [no]:  yes

Generating 2,048 bit RSA key pair and self-signed certificate (SHA256withRSA) with a validity of 9,125 days
	for: CN=Unknown, OU=Unknown, O=Unknown, L=Unknown, ST=Unknown, C=Unknown
Enter key password for <keyalias>
	(RETURN if same as keystore password):
Re-enter new password:
[Storing keystore.jks]

Warning:
The JKS keystore uses a proprietary format. It is recommended to migrate to PKCS12 which is an industry standard format using "keytool -importkeystore -srckeystore keystore.jks -destkeystore keystore.jks -deststoretype pkcs12".

As a TL;DR, you can just download a dummy certificate on the accompanying repository under should-be-private/keystore.jks, for testing purposes only. The keystore file is hugely important if you ever plan to submit your app to Google Play store: it’s the only way to assert you’re the rightful owner to provide new updates to your app.

File: keystore.jks
Keystore Password: keystorepassword
Keystore Key Alias: keyalias
Keystore Key Password: keypassword

4.3. Build APK

Make sure that you are serving the dist directory on http://127.0.0.1:8000 as explained above in Run a local server. Assuming you are using bash as your shell, from the root of your project, run:

EXPO_ANDROID_KEYSTORE_PASSWORD="keystorepassword" \
EXPO_ANDROID_KEY_PASSWORD="keypassword" \
turtle build:android \
  --type apk \
  --keystore-path ./should-be-private/keystore.jks \
  --keystore-alias "keyalias" \
  --allow-non-https-public-url \
  --public-url http://127.0.0.1:8000/android-index.json

Note that you need the flag --public-url to point to http://127.0.0.1:8000/android-index.json. In addition, it is also necessary to use the --type apk flag to produce an APK file since version 0.8.0 of turtle-cli.

The build may take some time:

Feb 5 08:29:51 turtle[11626] INFO:  Using manifest: {
  "name": "ExampleApplication",
  "slug": "ExampleApplication",
  "version": "1.0.0",
  "orientation": "portrait",
  "icon": "./assets/icon.png",
Feb 5 08:29:59 turtle[11626] INFO:  Starting a Gradle Daemon, 1 incompatible and 1 stopped Daemons could not be reused, use --status for details
  platform: "android"
  buildPhase: "running gradle"
  source: "stdout"
...

Once it finishes, you should see this output in your terminal:

Feb 5 08:34:22 turtle[11626] INFO:  copied build to ~/expo-apps/@anonymous__ExampleApplication-6d7e1749c5b64bd0851525b0c7eec780-signed.apk
  platform: "android"
  buildPhase: "copying build artifact"

This message gives you the location of your built .apk file. You can now move on to the Distribute and install section below if you are not interested in creating an .ipa file for iOS.

5. Create IPA file — iOS

First, verify that your local server is running, e.g.

$ curl http://127.0.0.1:8000/ios-index.json
{"name":"ExampleApplication","slug":"ExampleApplication","version":"1.0.0","orientation":"portrait","icon":"./assets/icon.png","splash":{"image":"./assets/splash.png","resizeMode":"contain","backgroundColor":"#ffffff","imageUrl":"http://127.0.0.1:8000/assets/201a91bd1740bb1d6a1dbad049310724"...

5.1. Prerequisites

For Turtle CLI to work correctly to create an .ipa file for iOS, you need to make sure your system is macOS and that the following dependencies are installed:

Xcode (version 11.4 or newer)
fastlane

Note: make sure that you have run Xcode at least once and that you have agreed to the license agreements.

For more details, see Expo’s documentation.

If you know which Expo SDK version you are going to use, you can run

$ turtle setup:ios --sdk-version <SDK-VERSION>

If it errors out, saying that you don’t have the right version of fastlane, try re-installing fastlane (guide). The version used in this article is fastlane 2.140.0.

This will take some time:

$ turtle setup:ios --sdk-version 40.0.1
Feb 4 09:18:03 turtle[48488] INFO:  shell app for SDK 40.0.1 doesn't exist, downloading...
  platform: "ios"
  buildPhase: "setting up environment"
downloading [                    ] 1% 8514.8s
...
...
Feb 4 09:24:58 turtle[48488] INFO:  it's all set!
  platform: "ios"
  buildPhase: "setting up environment"

In the meantime, you can move on to the next section.

5.2. Create Signing keys

This assumes you have an Apple Developer Account, which is a paid account.

To create your distribution certificate file, or .p12 file, you can follow this guide.

You will also need your Apple Team ID and a Provisioning Profile that you can generate through Xcode as well. This other guide covers in greater lengths what all these cerficates are for and how to obtain them.

Note that the provisioning profile expires in 6 days in my case, since I do not have an Apple Developer paid account.

Sadly, it is not possible to share example files.

5.3. Build IPA

Make sure that you are serving the dist directory on http://127.0.0.1:8000 as explained Run a local server. Assuming you are using bash as your shell, from the root of your project, run:

EXPO_IOS_DIST_P12_PASSWORD="<PASSWORD HERE>" \
turtle build:ios \
  --team-id YOUR_TEAM_ID \
  --dist-p12-path /path/to/your/dist/cert.p12 \
  --provisioning-profile-path /path/to/your/provisioning/profile.mobileprovision \
  --allow-non-https-public-url \
  --public-url http://127.0.0.1:8000/ios-index.json

Note that you need the flag --public-url to point to http://127.0.0.1:8000/ios-index.json.

Once the build finishes successfully, you should get the path to your .ipa file.

6. Distribute and install

6.1. on Android

Take your .apk and share it through some Google Drive link or other medium of your choice.

If you download this .apk file through an Android device, it should offer you to install the application on the device.

Trick: if the URL is really not friendly to type, and for whatever reason you have to type it manually, use a QR Code generator (e.g. http://www.barcode-generator.org/) and your device’s camera to simplify your life!

Alternatively, if you connect an Android device to your computer, you should be able to run:

$ adb devices
emulator-5554	device

to list all your connected Android devices and emulators. (In my case, only the emulator is “connected”.)

It is then possible to install the .apk file by running:

$ adb -s emulator-5554 install ~/expo-apps/@anonymous\\ExampleApplication-9be976cea1fb4651a6fa04d8432873eb-signed.apk
Performing Streamed Install
Success

6.2. on iOS

Caveat: I could not fully test this section, so my apologies if this does not work as intended.

Since you should have Xcode, the most promising solution is in this guide. It also mentions other ways to install the .ipa file.

That’s it for now, thank you for reading this far. You will find below the resources mentioned in this article.

If you have any questions or comments, please drop me a line on Twitter. I shall reply as soon as possible.

Stay tuned for more.

Resources

Expo: https://expo.io
Turtle CLI: https://github.com/expo/turtle#readme
Expo’s guide to Building Standalone apps: https://docs.expo.io/distribution/building-standalone-apps/
Configuring app.json: https://docs.expo.io/workflow/configuration
Expo docs to configure CI with Turtle CLI: https://docs.expo.io/distribution/turtle-cli
Expo docs to host application on your own servers: https://docs.expo.io/distribution/hosting-your-app/
How to create a keystore for Android: https://developer.android.com/studio/publish/app-signing#generate-key
Supporting GitHub repository: https://github.com/RobinCsl/build-standalone-expo-app/

Personal blog written by Robin Cussol
I like math and I like code. Oh, and writing too.

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