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MetaMask is a mobile wallet 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.
To learn how to contribute to the MetaMask codebase, visit our Contributor Docs.
- Architecture
- BigInt number migration (deprecated
app/util/number/index.jsburndown 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
- Storybook
- Miscellaneous
- Reassure Performance Testing (pilot)
MetaMask Mobile requires an Infura project ID to connect to blockchain networks.
- Grab the
.js.envfile from 1Password, ask around for the correct vault. This file contains theMM_INFURA_PROJECT_ID.
- Go to https://developer.metamask.io and create an account
- Generate an API key
- Add API key to
MM_INFURA_PROJECT_IDin.js.env.example - Rename
.js.env.exampleto.js.env - 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 on every push to main. 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
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:
# 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.
- Grab the
.js.envfile from 1Password, ask around for the correct vault. This file contains theGOOGLE_SERVICES_B64_ANDROIDandGOOGLE_SERVICES_B64_IOSsecrets that will be used to generate the relevant configuration files for IOS/Android. - 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)
- 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).
- Add Configuration Files
- Create/Update the
google-services.jsonandGoogleService-Info.plistfiles in: android/app/google-services.json(for Android)ios/GoogleServices/GoogleService-Info.plistdirectory (for iOS)
- Create/Update the
- 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.
