Getting started

Hardhat is an Ethereum development environment, designed for easy smart contract development. One of its most prominent features is extendability: you can easily add new plugins to your hardhat project.

Along with the official plugins, there are other plugins from the community that you can use with ZKsync Era.

To learn more about Hardhat itself, check out the official documentation.

This tutorial shows you how to setup a ZKsync Era Solidity project with Hardhat using the ZKsync CLI.

If you are using Vyper, check out the Vyper plugin documentation or the vyper-example in GitHub!

Project setup

To create a new project run the zksync-cli create command, passing a project name:

Solidity project

npx zksync-cli create demo --template hardhat_solidity

Vyper project

npx zksync-cli create demo --template hardhat_vyper

This command creates a demo folder and clones a Hardhat template project inside it. The downloaded project is already configured and contains all the required plugins.

Hardhat configuration

The hardhat.config.ts file contains some ZKsync Era specific configurations:

The ZKsync Era deployment and compiler plugin imports:

Solidity project

import '@matterlabs/hardhat-zksync';

The zksolc block contains the minimal configuration for the compiler.

  zksolc: {
    version: 'latest', // Uses latest available in https://github.com/matter-labs/zksolc-bin
    settings: {},
  },

Vyper project

import '@nomiclabs/hardhat-vyper';
import '@matterlabs/hardhat-zksync-vyper';
import '@matterlabs/hardhat-zksync-node';
import '@matterlabs/hardhat-zksync-deploy';

The zkvyper block contains the minimal configuration for the compiler.

  zkvyper: {
    version: 'latest', // Uses latest available in https://github.com/matter-labs/zkvyper-bin
    settings: {},
  },

Network

The default network is set to zkSyncSepoliaTestnet, but mainnet and local test node networks are also configured.

  defaultNetwork: 'zkSyncSepoliaTestnet',
  networks: {
    zkSyncSepoliaTestnet: {
      url: 'https://sepolia.era.zksync.dev',
      ethNetwork: 'sepolia',
      zksync: true,
      verifyURL: 'https://explorer.sepolia.era.zksync.dev/contract_verification',
    },
    zkSyncMainnet: {
      url: 'https://mainnet.era.zksync.io',
      ethNetwork: 'mainnet',
      zksync: true,
      verifyURL: 'https://zksync2-mainnet-explorer.zksync.io/contract_verification',
    },
    dockerizedNode: {
      url: 'http://localhost:3050',
      ethNetwork: 'http://localhost:8545',
      zksync: true,
    },
    inMemoryNode: {
      url: 'http://127.0.0.1:8011',
      ethNetwork: 'localhost', // in-memory node doesn't support eth node; removing this line will cause an error
      zksync: true,
    },
    hardhat: {
      zksync: true,
    },
  },

Set your Private Key

Rename .env.example to .env and set your private key:

WALLET_PRIVATE_KEY=YourPrivateKeyHere

Your private key will be used for paying the costs of deploying the smart contract.

Compile and deploy a contract

Smart contracts belong in the contracts folder.

1. To compile the contract, run

npm run compile

You'll see the following output:

Compiling 1 Solidity file
Successfully compiled 1 Solidity file
// Successfully compiled 1 Vyper file - Vyper project
✨  Done in 1.09s.

The artifacts-zk and cache-zk folders appear in the root directory (instead of the regular Hardhat's artifacts and cache). These folders contain the compilation artifacts (including contract's ABIs) and compiler cache files.

In the deploy folder, the deploy.ts script shows an example of how to deploy the Greeter.sol/Greeter.vy contract.

import { deployContract } from './utils';

// An example of a basic deploy script
// It will deploy a Greeter contract to selected network
// as well as verify it on Block Explorer if possible for the network
export default async function () {
  const contractArtifactName = 'Greeter';
  const constructorArguments = ['Hi there!'];
  await deployContract(contractArtifactName, constructorArguments);
}

2. To execute the deployment script run

npm run deploy

This script deploys the Greeting contract with the message "Hi there!" to ZKsync Sepolia Testnet.

You should see something like this:

Running deploy script for the Greeter contract
The deployment is estimated to cost 0.00579276320831943 ETH
constructor args:0x000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000094869207468657265210000000000000000000000000000000000000000000000
Greeter was deployed to 0x46f1d2d8A16DBD8b47e9D61175a826ac667288Be4D1293a22E8

✨  Done in 12.69s.

Congratulations! You have deployed a smart contract project to ZKsync Sepolia Testnet with Hardhat 🎉

Interact with the contract

The template project contains another script to interact with the contract.

1. Enter the address of the deployed Greeter contract in the CONTRACT_ADDRESS variable of the interact.ts script:
   interact.ts

   import * as hre from 'hardhat';
   import { getWallet } from './utils';
   import { ethers } from 'ethers';
   
   // Address of the contract to interact with
   const CONTRACT_ADDRESS = '';
   if (!CONTRACT_ADDRESS) throw '⛔️ Provide address of the contract to interact with!';
   
   // An example of a script to interact with the contract
   export default async function () {
     console.log(`Running script to interact with contract ${CONTRACT_ADDRESS}`);
   
     // Load compiled contract info
     const contractArtifact = await hre.artifacts.readArtifact('Greeter');
   
     // Initialize contract instance for interaction
     const contract = new ethers.Contract(
       CONTRACT_ADDRESS,
       contractArtifact.abi,
       getWallet() // Interact with the contract on behalf of this wallet
     );
   
     // Run contract read function
     const response = await contract.greet();
     console.log(`Current message is: ${response}`);
   
     // Run contract write function
     const transaction = await contract.setGreeting('Hello people!');
     console.log(`Transaction hash of setting new message: ${transaction.hash}`);
   
     // Wait until transaction is processed
     await transaction.wait();
   
     // Read message after transaction
     console.log(`The message now is: ${await contract.greet()}`);
   }
   

2. To execute the script, run:
   npmyarnpnpmbun

   npm run interact
   

   
   The script will:
   • Retrieve the message from the contract by calling the greet() method.
   • Update the greeting message in the contract with the setGreeting() method.
   • Retrieve the message from the contract again.
   
   You should see something like this:

   Running script to interact with contract Greeter
   The message is Hello there!
   Transaction to change the message is 0x12f16578A16DB0f47e9D61175a823ac214288Af
   The message now is Hello people!
   
   ✨  Done in 14.32s.
   

Learn more

• To learn more about the ZKsync Hardhat plugins check out the plugins documentation.
• If you want to know more about how to interact with ZKsync using Javascript, check out the zksync-ethers Javascript SDK documentation.