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MetaMask is a mobile wallet that provides easy access to websites that use the Ethereum blockchain.

For up to the minute news, follow our Twitter or Medium pages.

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

To learn how to contribute to the MetaMask codebase, visit our Contributor Docs.

• Architecture
• BigInt number migration (deprecated app/util/number/index.js burndown and ESLint allowlist)
• Expo Development Environment Setup
• Native Development Environment Setup
• Build Troubleshooting
• Component View Testing
• E2E Testing
• On-Ramp Provider Manual Testing
• Debugging
• Development Process
• Performance
• Release Build Profiling
• Internal Android distribution
• Storybook
• Miscellaneous
• Reassure Performance Testing (pilot)

MetaMask Mobile requires an Infura project ID to connect to blockchain networks.

1. Grab the .js.env file from 1Password, ask around for the correct vault. This file contains the MM_INFURA_PROJECT_ID.

1. Go to https://developer.metamask.io and create an account
2. Generate an API key
3. Add API key to MM_INFURA_PROJECT_ID in .js.env.example
4. Rename .js.env.example to .js.env
5. Rebuild the app

[!CAUTION]

Without an Infura project ID, the app cannot connect to blockchain networks.

Expo is the fastest way to start developing. With the Expo framework, developers don't need to compile the native side of the application as before, hence no need for any native environment setup, developers only need to download a precompiled development build and run the javascript bundler. The development build will then connect with the bundler to load the javascript code.

Install node, yarn v4 and watchman.

git clone git@github.com:MetaMask/metamask-mobile.git &&  cd metamask-mobile

yarn setup:expo

yarn watch

Expo development builds are produced by the Expo Dev Build GitHub Actions workflow. It runs on every push to main, but only actually compiles iOS/Android when the @expo/fingerprint hash of native code changed since the last build (plus a weekly Monday refresh so artifacts never go stale) — most pushes just reuse the existing build. This means the resolved run may be older than main HEAD; that's expected. Artifacts are stored as GitHub Actions artifacts (not Runway buckets).

Prerequisites: GitHub CLI (gh) authenticated with access to this repository (gh auth login).

Recommended — install the latest build on a simulator/emulator:

# iOS simulator yarn install:ios:dev  # Android emulator or device yarn install:android:dev

Download only (no install):

yarn install:ios:dev --skipInstall yarn install:android:dev --skipInstall

Re-runs skip the download when the GitHub Actions artifact digest matches a local cache under build/gh-expo-dev-build/. Force a fresh download with --force-download:

yarn install:ios:dev --force-download yarn install:android:dev --force-download

Artifacts land under build/ (MetaMask.app on iOS, metamask-dev.apk on Android). The workflow run id is saved to build/expo-dev-build-run-id.txt.

Manual download from GitHub Actions:

Note: since most runs skip the actual build (fingerprint unchanged), the most recent successful run may not have build artifacts attached — open the run and check for a build-dev job (skipped runs only have resolve-dev-build).

# List recent successful Expo Dev Build runs on main gh run list --repo MetaMask/metamask-mobile --workflow expo-dev-build.yml --branch main --status success --limit 5  mkdir -p build  # iOS simulator (.zip artifact → extract to MetaMask.app) gh run download RUN_ID --repo MetaMask/metamask-mobile    -n ios-app-main-dev-expo -D build mkdir -p build/MetaMask.app ditto -x -k build/metamask-simulator-*.zip build/MetaMask.app  # Android debug APK gh run download RUN_ID --repo MetaMask/metamask-mobile    -n android-apk-main-dev-expo -D build cp build/metamask-dev-main-*.apk build/metamask-dev.apk  # iOS physical device (.ipa — requires registered test device) gh run download RUN_ID --repo MetaMask/metamask-mobile    -n ios-ipa-main-dev-expo -D build

Use a specific workflow run instead of the latest:

yarn install:ios:dev --run RUN_ID yarn install:android:dev --run RUN_ID

(--run-id is also accepted.) Related: MCWP-683, supersedes PR #29891.

If on a simulator:

• use the initial expo screen that appears when starting the development to choose the bundler url
• OR press "a" for Android or "i" for iOS on the terminal where the bundler is running

If on a physical device:

• Use the camera app to scan the QR code presented by the bundler running on the terminal

That's it! This will work for any javascript development, if you need to develop or modify native code please see the next section.

If developing or modifying native code or installing any library that introduces or uses native code, it is not possible to use an Expo precompiled development build as you need to compile the native side of the application again. To do so, please follow the steps stated in this section.

Before running the app for native development, make sure your development environment has all the required tools. Several of these tools (ie Node and Ruby) may require specific versions in order to successfully build the app.

Setup your development environment

Clone the project

git clone git@github.com:MetaMask/metamask-mobile.git &&  cd metamask-mobile

MetaMask uses Firebase Cloud Messaging (FCM) to enable app communications. To integrate FCM, you'll need configuration files for both iOS and Android platforms.

1. Grab the .js.env file from 1Password, ask around for the correct vault. This file contains the GOOGLE_SERVICES_B64_ANDROID and GOOGLE_SERVICES_B64_IOS secrets that will be used to generate the relevant configuration files for IOS/Android.
2. Install and run & start the application as documented below.

As an external contributor, you need to provide your own Firebase project configuration files:

• GoogleService-Info.plist (iOS)
• google-services.json (Android)

1. Create a Free Firebase Project
   • Set up a Firebase project in the Firebase Console.
   • Configure the project with a client package name matching io.metamask (IMPORTANT).
2. Add Configuration Files
   • Create/Update the google-services.json and GoogleService-Info.plist files in:
   • android/app/google-services.json (for Android)
   • ios/GoogleServices/GoogleService-Info.plist directory (for iOS)
3. Create the correct base64 environments variables.

# Generate Android Base64 Version of Google Services export GOOGLE_SERVICES_B64_ANDROID="$(base64 -w0 -i ./android/app/google-services.json)" && echo "export GOOGLE_SERVICES_B64_ANDROID="$GOOGLE_SERVICES_B64_ANDROID"" | tee -a .js.env  # Generate IOS Base64 Version of Google Services export GOOGLE_SERVICES_B64_IOS="$(base64 -w0 -i ./ios/GoogleServices/GoogleService-Info.plist)" && echo "export GOOGLE_SERVICES_B64_IOS="$GOOGLE_SERVICES_B64_IOS"" | tee -a .js.env

[!CAUTION]

In case you don't provide your own Firebase project config file or run the steps above, you will face the error No matching client found for package name 'io.metamask'.

In case of any doubt, please follow the instructions in the link below to get your Firebase project config file. Firebase Project Quickstart

yarn setup

Not the usual install command, this will run scripts and a lengthy postinstall flow

Run Metro bundler

yarn watch

Like a local server for the app

Run on a iOS device

yarn start:ios

Run on an Android device

yarn start:android

AI coding agents (Cursor, Claude Code, Codex) consume shared skills from the MetaMask/skills repo, with an optional private overlay from Consensys/skills. Per ADR #57 this content is not committed here — yarn skills syncs it on demand into local-only paths under .cursor/, .claude/, and .agents/.

Zero-config setup:

yarn install # refreshes the MetaMask/skills cache via the shared @metamask/skills CLI yarn skills  # syncs all default skills through metamask-skills sync

Optional local configuration:

cp .skills.local.example .skills.local # edit .skills.local to set SKILLS_DOMAINS or override skills source paths yarn skills --select                         # interactively pick domains SKILLS_DOMAINS=perps,testing yarn skills      # one-off domain override

Use .skills.local for persistent skills configuration. Shell environment variables with the same names are supported for one-off or CI overrides and take precedence.

Skipping yarn skills is fine — it only affects agent tooling, not the app build. The repo uses the shared @metamask/skills package so sync/cache behavior stays uniform across MetaMask packages. To opt into best-effort regeneration during install/setup, set SKILLS_AUTO_UPDATE=1 in your shell or .skills.local.

This project uses Husky to run pre-commit hooks that automatically format and lint your code before commits. The pre-commit hook runs lint-staged which executes:

• Prettier - Code formatting for *.{js,jsx,ts,tsx,json,feature} files
• ESLint - Linting and auto-fixing for *.{js,jsx,ts,tsx} files

If you need to disable Husky pre-commit hooks temporarily (e.g., for emergency commits or debugging), you have several options:

git commit --no-verify -m "your commit message"

# Disable for current session export HUSKY=0 git commit -m "your commit message"  # Or disable for a single command HUSKY=0 git commit -m "your commit message"

Note: While these methods allow you to bypass the pre-commit hooks, remember that the CI/CD pipeline will still run linting checks. It's recommended to fix linting issues before pushing your changes to avoid build failures.