> For the complete documentation index, see [llms.txt](https://docs.cronos.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.cronos.com/for-dapp-developers/framework-integration/hardhat-3-integration.md). # Hardhat 3 Integration Build a Hardhat 3 project from scratch, configure it for Cronos EVM, and deploy a sample contract with Hardhat Ignition. ## Hardhat 3 Hardhat 3 is the recommended toolchain for new Cronos projects. It uses `Hardhat Ignition` for declarative deploymentsand an encrypted keystore so your private key never touches a file in your repo, and it lets you pick your test stack at init time — `viem` with `node:test`, or `Mocha` with `Ethers.js`. ### Prerequisites * Node.js 22.13.0 or later * A wallet private key: With a small amount of CRO to pay for gas fees. (For testnet TCRO, use the faucet at[ https://faucet.cronos.com/](https://faucet.cronos.com/).) * An RPC endpoint: See details [here](/introduction/introduction.md). * A Cronos Explorer API key, see how to obtain it [here](/for-dapp-developers/block-explorer-and-api-keys.md#creating-account-and-getting-api-key-cronos-explorer). ### Step 1. Create and initialize the project ```bash npx hardhat --init ``` `--init` is an interactive wizard. Choose: * Where would you like to initialize the project? -> Your project path, for example `my-cronos-project` * What type of project? → `A TypeScript Hardhat project using Node Test Runner and Viem` or `A TypeScript Hardhat project using Mocha and Ethers.js` . * Accept the suggested `package.json` and dependency install. ### Step 2. Write your contract The wizard writes a sample `Counter` contract at `my-cronos-project/contracts/Counter.sol` . You can remove it and add your contracts to `my-cronos-project/contracts/`. ### Step 2.1. Install Dependencies For example, to add `OpenZeppelin` as a dependency: ```bash npm install @openzeppelin/contracts ``` ### Step 3. Store your secrets Hardhat 3 ships an encrypted keystore. Use it instead of a `.env` file. The value is stored outside your project, encrypted with a password you choose. ```bash npx hardhat keystore set PRIVATE_KEY ``` You will be prompted for a keystore password (first time only) and then for the value. Useful companions: ```bash npx hardhat keystore list # show which keys are set npx hardhat keystore get PRIVATE_KEY npx hardhat keystore delete PRIVATE_KEY npx hardhat keystore path # where the encrypted file lives ``` ### Step 4. Configure Cronos Network In your `hardhat.config.ts` config Cronos networks: {% code title="hardhat.config.ts" lineNumbers="true" %} ```typescript const config: HardhatUserConfig = { plugins: [...], solidity: { ... }, networks: { cronos: { type: "http", chainType: "l1", url: "https://evm.cronos.com/", chainId: 25, accounts: [configVariable("PRIVATE_KEY")], gasPrice: 10100000000000, }, cronosTestnet: { type: "http", chainType: "l1", url: "https://evm-t3.cronos.com/", chainId: 338, accounts: [configVariable("PRIVATE_KEY")], gasPrice: 10100000000000, }, }, }; export default config; ``` {% endcode %} ### Step 5. Compile ```bash npx hardhat compile ``` ### Step 6. Test The wizard created a sample test contract at `my-cronos-project/contracts/Counter.t.sol` , and a sample test script at `my-cronos-project/test/Counter.ts` : * `contract/Counter.t.sol`: Written in Solidity. It runs directly on the Ethereum Virtual Machine (EVM) using Foundry (Forge). * `test/Counter.ts`**:** Written in TypeScript. It runs in a Node.js environment. Check the differences between two test approaches at [Hardhat 3 document](https://hardhat.org/docs/guides/testing). To run all the tests: ```bash npx hardhat test ``` To run each type of test: ```bash npx hardhat test solidity # Solidity tests only npx hardhat test nodejs # TypeScript & viem tests only npx hardhat test mocha # Mocha tests only ``` ### Step 7. Deploy Hardhat 3 deploys through Ignition modules — declarative descriptions of what to deploy, so re-running a deployment resumes instead of duplicating. The wizard created a sample at `ignition/modules/Counter.ts` . To run the script: ```bash npx hardhat ignition deploy ignition/modules/Counter.ts --network cronosTestnet ``` Ignition prints the deployed address on success. To deploy to mainnet, swap `--network cronosTestnet` for `--network cronos`. ### Step 8. Verify `hardhat-verify` is already included as part of the template project. If you want to add the plugin manually: ```bash npm add --save-dev @nomicfoundation/hardhat-verify ``` In your `hardhat.config.ts` add: ```typescript import hardhatVerify from "@nomicfoundation/hardhat-verify"; const networkArg = process.argv[process.argv.indexOf('--network') + 1] ?? 'hardhat'; export default defineConfig({ plugins: [...,hardhatVerify,], ... chainDescriptors: { 25: { name: "cronos", blockExplorers: { etherscan: { name: "Cronos Explorer", url: "https://explorer.cronos.com", apiUrl: "https://explorer-api.cronos.org/mainnet/api/v2", }, }, }, 338: { name: "cronosTestnet", blockExplorers: { etherscan: { name: "Cronos Explorer Testnet", url: "https://explorer.cronos.com/testnet", apiUrl: "https://explorer-api.cronos.org/testnet/api/v2", }, }, }, }, verify: { etherscan: { apiKey: networkArg === "cronos" ? ?? "" : networkArg === "cronosTestnet" ? ?? "" : "", }, }, }); ``` In your terminal: ```bash npx hardhat verify --network cronosTestnet
``` This command will verify the contract in both Cronos Explorer and Sourcify, to verify it only in Cronos Explorer: ```bash npx hardhat verify etherscan --network cronosTestnet
``` Or add below config to `hardhat.config.ts` : ```typescript verify: { blockscout: { enabled: false, }, sourcify: { enabled: false, }, }, ``` Alternatively, you can deploy and verify the contract in a single command: ```bash npx hardhat ignition deploy ignition/modules/Counter.ts --network cronosTestnet --verify ``` To verify the contract in mainnet, swap `--network cronosTestnet` for `--network cronos`.