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5.8K Stars 2.3K Forks Other 13.1K Commits 974 Opened issues


:globe_with_meridians: :electric_plug: The MetaMask browser extension enables browsing Ethereum blockchain enabled websites

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Contributors list

MetaMask Browser Extension

Hey! We are hiring JavaScript Engineers! Apply here!

You can find the latest version of MetaMask on our official website. For help using MetaMask, visit our User Support Site.

For general questions, feature requests, or developer questions, visit our Community Forum.

MetaMask supports Firefox, Google Chrome, and Chromium-based browsers. We recommend using the latest available browser version.

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 project itself, visit our Internal Docs.

Building locally

  • Install Node.js version 14
    • If you are using nvm (recommended) running
      nvm use
      will automatically choose the right node version for you.
  • Install Yarn
  • Install dependencies:
    yarn setup
    (not the usual install command)
  • Copy the
    file to
    • Replace the
      value with your own personal Infura Project ID.
    • If debugging MetaMetrics, you'll need to add a value for
      Segment write key.
  • Build the project to the
    folder with
    yarn dist

Uncompressed builds can be found in

, compressed builds can be found in
once they're built.

See the build system readme for build system usage information.


Development builds

To start a development build (e.g. with logging and file watching) run

yarn start

To start the React DevTools and Redux DevTools Extension alongside the app, use

yarn start:dev
. - React DevTools will open in a separate window; no browser extension is required - Redux DevTools will need to be installed as a browser extension. Open the Redux Remote Devtools to access Redux state logs. This can be done by either right clicking within the web browser to bring up the context menu, expanding the Redux DevTools panel and clicking Open Remote DevTools OR clicking the Redux DevTools extension icon and clicking Open Remote DevTools. - You will also need to check the "Use custom (local) server" checkbox in the Remote DevTools Settings, using the default server configuration (host
, port
, secure connection checkbox unchecked)

Test site can be used to execute different user flows.

Running Unit Tests and Linting

Run unit tests and the linter with

yarn test
. To run just unit tests, run
yarn test:unit

You can run the linter by itself with

yarn lint
, and you can automatically fix some lint problems with
yarn lint:fix
. You can also run these two commands just on your local changes to save time with
yarn lint:changed
yarn lint:changed:fix

Running E2E Tests

Our e2e test suite can be run on either Firefox or Chrome. In either case, start by creating a test build by running

yarn build:test

Firefox e2e tests can be run with

yarn test:e2e:firefox

Chrome e2e tests can be run with

yarn test:e2e:chrome
, but they will only work if you have Chrome v79 installed. Update the
package to a version matching your local Chrome installation to run e2e tests on newer Chrome versions.

Changing dependencies

Whenever you change dependencies (adding, removing, or updating, either in

), there are various files that must be kept up-to-date.
  • yarn.lock
    • Run
      yarn setup
      again after your changes to ensure
      has been properly updated.
  • The
    configuration in
    • Run
      yarn allow-scripts auto
      to update the
      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.
  • The LavaMoat auto-generated policy in
    • Run
      yarn lavamoat:auto
      to re-generate this policy file. Review the changes to determine whether the access granted to each package seems appropriate.
    • Unfortunately,
      yarn lavamoat:auto
      will behave inconsistently on different platforms. macOS and Windows users may see extraneous changes relating to optional dependencies.


Architecture Diagram


yarn start

Build for Publishing

yarn dist

Other Docs

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