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'.
--leave-running Leaves the browser running after a test fails, along with anything else
that the test used (ganache, the test dapp, etc.).
--retries Set how many times the test should be retried upon failure. Default is 0.
```
An example for running `account-details` testcase with chrome and leaving the browser open would be:
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 LavaMoat policy files. The _tl;dr_ is to run `yarn lavamoat:auto` to update these files, but there can be devils in the details. Continue reading for more information.
* There are two sets of LavaMoat policy files:
* The production LavaMoat policy files (`lavamoat/browserify/*/policy.json`), which are re-generated using `yarn lavamoat:background:auto`.
* These should be regenerated whenever the production dependencies for the background change.
* The build system LavaMoat policy file (`lavamoat/build-system/policy.json`), which is re-generated using `yarn lavamoat:build:auto`.
* This should be regenerated whenever the dependencies used by the build system itself change.
* Whenever you regenerate a 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.
* Keep in mind that any kind of dynamic import or dynamic use of globals may elude LavaMoat's static analysis.
Refer to the LavaMoat documentation or ask for help if you run into any issues.
- [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)
