Using Hardhat

Hardhat is a full-featured development environment for contract compilation, deployment and verification. The Hardhat Etherscan plugin supports contract verification on kcc scan.

Get Started

1) Install Hardhat

If you are starting from scratch, create an npm project by going to an empty folder, running npm init, and following the instructions. Recommend npm 7 or higher.

Once your project is ready:

npm instructions

npm install --save-dev hardhat

yarn instructions

yarn add --dev hardhat

pnpm instructions

pnpm add -D hardhat

2) Create a project

Run npx hardhat in your project folder and follow the instructions to create (more info here).

3) Install plugin

Install the hardhat-etherscan plugin (requires v3.0.0+).


npm install --save-dev @nomiclabs/hardhat-etherscan


yarn add --dev @nomiclabs/hardhat-etherscan


pnpm add -D @nomiclabs/hardhat-etherscan

4) Add plugin reference to config file

Add the following statement to your hardhat.config.js.


If using TypeScript, add this to your hardhat.config.ts. More info on using typescript with hardhat available here.

import "@nomiclabs/hardhat-etherscan";

Config File

Your basic Hardhat config file (hardhat.config.js or hardhat.config.ts) will be setup to support the network you are working on. In this example we use the kcc test network and a .js file.

You can add a customChains object to the config file. It includes:

  • chainID - Network chain ID

  • apiURL - Block explorer API URL

  • browserURL - Block explorer URL


let secret = require("./secret");

module.exports = {
  solidity: "0.8.17",
  networks: {
    kt: {
      url: '',
      accounts: [secret.key],
    km: {
      url: '',
      accounts: [secret.key],
  etherscan: {
    apiKey: {
      kt: "abc",
      km: "abc"
    customChains: [
        network: "km",
        chainId: 321,
        urls: {
          apiURL: "",
          browserURL: ""
        network: "kt",
        chainId: 322,
        urls: {
          apiURL: "",
          browserURL: ""

Deploy and Verify


npx hardhat run scripts/deploy.js --network kt
Contract deployed to: 0x3F0A49981D3204A8E7bD7871aDEFBC6379A05410


You can include constructor arguments with the verify task.

npx hardhat verify --network <network> DEPLOYED_CONTRACT_ADDRESS "Constructor argument"

KCC Testnet example (has constructors).

D:\hardhat>npx hardhat verify --network kt 0x3F0A49981D3204A8E7bD7871aDEFBC6379A05410 "0x0576a174D229E3cFA37253523E645A78A0C91B57,0xae3DB39196012a7bF6D38737192F260cdFE1E7Ec"
Nothing to compile
Compiling 1 file with 0.8.0
Successfully submitted source code for contract
contracts/KCCPaymaster.sol:KCCPaymaster at 0x3F0A49981D3204A8E7bD7871aDEFBC6379A05410
for verification on the block explorer. Waiting for verification result...

Successfully verified contract KCCPaymaster on Etherscan.

Note the verify task will not be listed in the available tasks lists at npx hardhat --config but should work as expected.

If not, check you have the minimum required version of the nomiclabs-hardhat-etherscan plugin (v3.0.0+) installed

Confirm Verification on KCC Scan

Go to KCC Scan instance and paste the contract address into the search bar. If verified, the code tab will display a green checkmark.

Selecting the Code tab will provide additional information about your contract.


Learn more about plugin configs, troubleshooting etc. at

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