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

// hardhat.config.ts
import '@nomicfoundation/hardhat-verify';

export default {
  // ... other config
  etherscan: {
    apiKey: {
      baseSepolia: process.env.BASESCAN_API_KEY,
      baseMainnet: process.env.BASESCAN_API_KEY,
    },
  },
};

# Testnet
npx hardhat verify --network baseSepolia CONTRACT_ADDRESS

# Mainnet
npx hardhat verify --network baseMainnet CONTRACT_ADDRESS

npx hardhat flatten contracts/Shield.sol > Shield_flat.sol

curl "https://api.basescan.org/api?module=contract&action=getabi&address=CONTRACT_ADDRESS"

{
  "status": "1",
  "message": "OK",
  "result": "[{\"constant\":true,\"inputs\":[]..."
}