Mobile web browser providing access to websites that use the Ethereum blockchain
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MetaMask is a mobile web browser that provides easy access to websites that use the Ethereum blockchain.

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To learn how to develop MetaMask-compatible applications, visit our Developer Docs.

MetaMask Mobile

Building Locally

The code is built using React-Native and running code locally requires a Mac or Linux OS.

  • Install sentry-cli tools: brew install getsentry/tools/sentry-cli

  • Install Node.js version 14 (latest stable) and yarn@1 (latest)

    • If you are using nvm (recommended) running nvm use will automatically choose the right node version for you.
  • Install the shared React Native dependencies (React Native CLI, not Expo CLI)

  • Install cocoapods by running:

sudo gem install cocoapods
  • MetaMask Only: Rename the .*.env.example files (remove the .example) in the root of the project and fill in the appropriate values for each key. Get the values from another MetaMask Mobile developer.

  • Clone this repo and install our dependencies:

git clone ...
cd metamask-mobile
yarn setup # not the usual install command, this will run a lengthy postinstall flow
cd ios && pod install && cd .. # install pods for iOS
  • Non-MetaMask Only: In the project root folder run
  cp .ios.env.example .ios.env && \
  cp .android.env.example .android.env && \
  cp .js.env.example .js.env
  • Non-MetaMask Only: Create an account and generate your own API key at Infura in order to connect to main and test nets. Fill MM_INFURA_PROJECT_ID in .js.env. (App will run without it, but will not be able to connect to actual network.)

  • Then, in one terminal, run:

yarn watch


  • Install the Android SDK, via Android Studio.
    • MetaMask Only: To create production builds, you need to install Google Play Licensing Library via the SDK Manager in Android Studio.
  • Install the Android NDK, via Android Studio's SDK Manager.
    • In the SDK Manager, select the SDK Tools tab and install NDK version 21.4.7075529. You'll need to click "Show Package Details" in order to select the appropriate version.
  • Linux only:
    • Ensure that you have the secret-tool binary on your machine.
      • Part of the libsecret-tools package on Debian/Ubuntu based distributions.
  • Install the correct emulator
  • Finally, start the emulator from Android Studio, and run:
yarn start:android


  • Install the iOS dependencies
  • Install the correct simulator
    • iOS OS Version: Latest, unless told otherwise
    • Device: iPhone 11 Pro
yarn start:ios

Build Troubleshooting

Unfortunately, the build system may fail to pick up local changes, such as installing new NPM packages or yarn linking a dependency. If the app is behaving strangely or not picking up your local changes, it may be due to build issues. To ensure that you're starting with a clean slate, close all emulators/simulators, stop the yarn watch process, and run:

yarn clean

# if you're going to `yarn link` any packages,
# do that here, before the next command

yarn watch:clean

# ...and then, in another terminal

yarn start:ios

# or

yarn start:android

If yarn link fails after going through these steps, try directly yarn adding the local files instead.


First, make sure you have the following running:

  • yarn watch
  • Your Android emulator or iOS simulator
  • yarn start:android or yarn start:ios

Next, install the Flipper desktop app (verified working with v0.127.0)

  • Once Flipper is installed, configure your system as follows:
    • Install react-devtools: npm i -g react-devtools@4.22.1
    • Update Android SDK location settings by accessing Flipper's settings via the Gear Icon -> Settings
      • Example SDK path: /Users/<USER_NAME>/Library/Android/sdk

Finally, check that the debugger is working:

  • Open your emulator or simulator alongside the Flipper app
  • Flipper should auto-detect the device and the application to debug
  • You should now be able to access features such as Logs

Debugging Physical iOS devices

  • Debugging physical iOS devices requires idb to be installed, which consists of 2 parts
  • Install the two idb parts:
    1. brew tap facebook/fb & brew install idb-companion
    2. pip3.9 install fb-idb (This step may require that you install python3 via python -m pip3 install --upgrade pip)


Running Tests

Unit Tests

yarn test:unit

E2E Tests (iOS)

First, follow the instructions here to install applesimutils. Then:

yarn test:e2e:ios

E2E Tests (Android)

yarn test:e2e:android

Changing dependencies

Whenever you change dependencies (adding, removing, or updating, either in package.json or yarn.lock), there are various files that must be kept up-to-date.

  • yarn.lock:
    • Run yarn setup again after your changes to ensure yarn.lock has been properly updated.
  • The allow-scripts configuration in package.json
    • Run yarn allow-scripts auto to update the allow-scripts configuration automatically. This config determines whether the package's install/postinstall scripts are allowed to run. Review each new package to determine whether the install script needs to run or not, testing if necessary.
    • Unfortunately, yarn allow-scripts auto will behave inconsistently on different platforms. macOS and Windows users may see extraneous changes relating to optional dependencies.


To get a better understanding of the internal architecture of this app take a look at this diagram.