MetaMask Snaps is a system that allows anyone to safely expand the capabilities of MetaMask. A snap is a program that we run in an isolated environment that can customize the wallet experience.
Truffle Boxes are helpful boilerplates that allow you to focus on what makes your dapp unique. In addition to Truffle, Truffle Boxes can contain other helpful modules, Solidity contracts & libraries, front-end views and more; all the way up to complete example dapps. This box makes it easy to deploy and test contracts with a local Ganache instance, which can be used to test transaction insight snaps or smart contract account snaps.
Snaps should work with the latest LTS version of Node.js, but we recommend using the version specified in the
.nvmrc file. If you use nvm you can easily switch to the right version by calling
nvm use at the root of the project.
This box uses Yarn v3.x. If you are using Node 16 or later you can enable it with
To interact with (your) snaps, you will need to install MetaMask Flask, a canary distribution for developers that provides access to upcoming features. You should install Flask in a separate browser profile from any existing MetaMask installation.
Before using this box, install Truffle and Ganache globally:
npm install -g truffle ganache
You can install this box with Truffle:
truffle unbox metamask/snap-box <dir_name>
Alternatively, you can clone the snap-box repository using this GitHub template.
You can add your own Infura API key to fork the Ethereum blockchain in your local instance of Ganache. Copy the
.env.dist file in
packages/truffle/ to a new file
.env and update the
INFURA_PROJECT_ID variable with your API key.
Then, you can take your Secret Recovery Phrase from MetaMask Flask and put it as the
MNEMONIC_PHRASE in this same file. This will make your first Ethereum account as the deployer of the test contracts in Ganache and provide you with a balance for the first 10 accounts for local testing. Remember, you should never share your Secret Recovery Phrase with anyone, and you should never use a Secret Recovery Phrase from any version of MetaMask that you use to custody real funds. This
.env file is never and should never be uploaded to GitHub (it is explicitly excluded in
.gitignore). This is only for testing locally with Ganache.
Alternatively, you can take the Mnemonic Phrase generated by Truffle and use that as your Secret Recovery Phrase when setting up MetaMask Flask. This will guarantee that your transaction history is empty each time you start testing.
Then, setup the development environment from the main directory:
yarn install && yarn start
You are now ready to start modifying the packages to build your snap. You can put smart contracts in
packages/truffle/contracts and modify the files in
packages/site. Connect MetaMask to your local Ganache instance by going into your settings and changing the network to "Localhost 8545" (if you cannot see it, make sure to click "Show test networks").