Verify Smart Contract using Hardhat

warning

As of block height 31,056,500 (March 26, 2025, 3:00 AM UTC), Celo is no longer a standalone Layer 1 blockchain—it is now an Ethereum Layer 2! Some documentation may be outdated as updates are in progress. If you encounter issues, please file a bug report.

For the most up-to-date information, refer to our Celo L2 documentation.

Verifying a smart contract allows developers to review your code from within the CeloScan Block Explorer

tip

If you use Celo Composer all the configuration is done for you out of the box, all you need is the CeloScan API keys!

Prerequisites

Before the installation steps you need to have your hardhat project initialized using the command

npx hardhat init

Make sure to have dependencies installed and the hardhat config file is importing @nomicfoundation/hardhat-toolbox

Hardhat Configuration

Add the following configuration to the config object in hardhat.config.js.

    networks: {
        alfajores: {
            // can be replaced with the RPC url of your choice.
            url: "https://alfajores-forno.celo-testnet.org",
            accounts: [
                "<YOUR_PRIVATE_KEY>"
            ],
        },
        celo: {
            url: "https://forno.celo.org",
            accounts: [
                "<YOUR_PRIVATE_KEY>"
            ],
        }
    },
    etherscan: {
        apiKey: {
            alfajores: "<CELOSCAN_API_KEY>",
            celo: "<CELOSCAN_API_KEY>"
        },
        customChains: [
            {
                network: "alfajores",
                chainId: 44787,
                urls: {
                    apiURL: "https://api-alfajores.celoscan.io/api",
                    browserURL: "https://alfajores.celoscan.io",
                },
            },
            {
                network: "celo",
                chainId: 42220,
                urls: {
                    apiURL: "https://api.celoscan.io/api",
                    browserURL: "https://celoscan.io/",
                },
            },
        ]
    },

Verifying Contracts

Use the following command (Make sure your contracts are compiled before verification)

Alfajores Testnet

npx hardhat verify [CONTRACT_ADDRESS] [...CONSTRUCTOR_ARGS] --network alfajores

Celo Mainnet

npx hardhat verify [CONTRACT_ADDRESS] [CONSTRUCTOR_ARGS] --network celo