You can find the latest version of MetaMask on [our official website](https://metamask.io/). For help using MetaMask, visit our [User Support Site](https://metamask.zendesk.com/hc/en-us).
To learn how to contribute to the MetaMask project itself, visit our [Internal Docs](https://github.com/MetaMask/metamask-extension/tree/develop/docs).
- If you are using [nvm](https://github.com/creationix/nvm#installation) (recommended) running `nvm use` will automatically choose the right node version for you.
- If debugging MetaMetrics, you'll need to add a value for `SEGMENT_WRITE_KEY` [Segment write key](https://segment.com/docs/connections/find-writekey/), see [Developing on MetaMask - Segment](./development/README.md#segment).
- If debugging unhandled exceptions, you'll need to add a value for `SENTRY_DSN` [Sentry Dsn](https://docs.sentry.io/product/sentry-basics/dsn-explainer/), see [Developing on MetaMask - Sentry](./development/README.md#sentry).
To start the [React DevTools](https://github.com/facebook/react-devtools), run `yarn devtools:react` with a development build installed in a browser. This will open in a separate window; no browser extension is required.
To start the [Redux DevTools Extension](https://github.com/reduxjs/redux-devtools/tree/main/extension):
- Install the package `remotedev-server` globally (e.g. `yarn global add remotedev-server`)
- Install the Redux Devtools extension.
- Open the Redux DevTools extension and check the "Use custom (local) server" checkbox in the Remote DevTools Settings, using the default server configuration (host `localhost`, port `8000`, secure connection checkbox unchecked).
Then run the command `yarn devtools:redux` with a development build installed in a browser. This will enable you to use the Redux DevTools extension to inspect MetaMask.
To create a development build and run both of these tools simultaneously, run `yarn start:dev`.
#### Test Dapp
[This test site](https://metamask.github.io/test-dapp/) can be used to execute different user flows.
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` and `yarn lint:changed:fix` respectively.
### 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`.
- Chrome e2e tests can be run with `yarn test:e2e:chrome`. The `chromedriver` package major version must match the major version of your local Chrome installation. If they don't match, update whichever is behind before running Chrome e2e tests.
- Single e2e tests can be run with `yarn test:e2e:single test/e2e/tests/TEST_NAME.spec.js` along with the options below.
```console
--browser Set the browser used; either 'chrome' or 'firefox'.
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.
* The production LavaMoat policy files (`lavamoat/browserify/*/policy.json`), which are re-generated using `yarn lavamoat:background:auto`. Add `--help` for usage.
- [Extend MetaMask's features w/ MetaMask Snaps.](https://docs.metamask.io/guide/snaps.html)
- [Prompt your users to add and switch to a new network.](https://medium.com/metamask/connect-users-to-layer-2-networks-with-the-metamask-custom-networks-api-d0873fac51e5)
- [Change the logo that appears when your dapp connects to MetaMask.](https://docs.metamask.io/guide/defining-your-icon.html)
