Verify a contract

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

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-verify plugin (requires v3.0.0+).


npm install --save-dev @nomicfoundation/hardhat-verify


yarn add --dev @nomicfoundation/hardhat-verify

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 "@nomicfoundation/hardhat-verify";

Config Custom Networks

Your basic Hardhat config file (hardhat.config.js or hardhat.config.ts) will be setup to support Conla Testnet.

You have to specify the explorer details under a customChains object. It includes:

  • chainID - 11118

  • apiURL -

  • browserURL -

import { HardhatUserConfig } from "hardhat/config";
import "@nomicfoundation/hardhat-toolbox";
import "@nomicfoundation/hardhat-verify";

const PRIVATE_KEY = vars.get("PRIVATE_KEY");

const config: HardhatUserConfig = {
  solidity: "0.8.24",
  networks: {
    conla-testnet: {
      url: '',
      accounts: [PRIVATE_KEY],
  etherscan: {
    apiKey: {
      // Is not required. Can be any non-empty string
      sepolia: "abc"
    customChains: [
        network: "conla-testnet",
        chainId: 11118,
        urls: {
          apiURL: "",
          browserURL: "",
  sourcify: {
    enabled: false

export default config;

Deploy and Verify

For deployment we will use Hardhat Ignition - built-in Hardhat deployment system.


D:\hard_hat>npx hardhat ignition deploy ./ignition/modules/Lock.ts --network conla-testnet
✔ Confirm deploy to network conla-testnet (11118)? … yes
Compiled 1 Solidity file successfully (evm target: paris).
Hardhat Ignition 🚀

Deploying [ LockModule ]

Batch #1
  Executed LockModule#Lock

[ LockModule ] successfully deployed 🚀

Deployed Addresses

LockModule#Lock - 0x15447991b46862f6cF9a5dB358a923f768a9Fadb


The plugin requires you to include constructor arguments with the verify task and ensures that they correspond to expected ABI signature. However, Conla Explorer ignores those arguments, so you may specify any values that correspond to the ABI.

npx hardhat verify --network conla-testnet DEPLOYED_CONTRACT_ADDRESS "Constructor argument 1"


D:\hard_hat>npx hardhat verify --network conla-testnet 0x15447991b46862f6cF9a5dB358a923f768a9Fadb 1234
Successfully submitted source code for contract
contracts/Lock.sol:Lock at 0x15447991b46862f6cF9a5dB358a923f768a9Fadb
for verification on the block explorer. Waiting for verification result...

Successfully verified contract Lock on the block explorer.

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

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

Automatically verified contracts

Sometimes the contract may be automatically verified via Ethereum Bytecode Database service. In that case you may see the following response:

The contract 0x15447991b46862f6cF9a5dB358a923f768a9Fadb has already been verified on Etherscan.

In that case, you may try to enforce using --force flag*.

It prevents Hardhat to check if the contract is already verified, and force it to send verification request anyway. Notice, that it is helpful only if the contract was automatically verified partially. That way, a new verification sources would be saved. If the contract was fully verified already, that just returns an error.

npx hardhat verify --network conla-testnet DEPLOYED_CONTRACT_ADDRESS "Constructor argument 1" --force
  • The flag is available starting from @nomicfoundation/hardhat-verify@2.0.7

Confirm Verification on Conla Explorer

Go to Conla Explorer and paste the contract address into the search bar.

Scroll down to see verified status. A green checkmark ✅ means the contract is verified.

If your screen size is limited, you may need to click the 3 dots to view and click through to the contract.

Scroll down to see and interact with the contract code.

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