Contract Verification

Where To Verify

Blast has a several block explorers to choose from. Which explorer you choose to spend the most time with is a matter of personal preference, but one common question from new builders is where do I verify my contracts?. Out of the available options, blastscan.io and blastexplorer.io are where most people verify their contracts, so that’s what we’d recommend.

The following guide will help you steer clear common issues while verifying your contracts with Foundry and Hardhat.

Do I Need An API Key?

Whether or not you need valid API key depends on (a) which network you’re using and (b) which API you’re targeting. Blastexplorer’s API will let you verify on testnet and mainnet without requiring a valid API key, but blastscan does require one when verifying on mainnet. You can get a blastscan API key by creating a free account here, and navigating to the “API-KEYs” section of your profile.

Explorer	Testnet	Mainnet
blastscan.io	no	yes
blastexplorer.io	no	no

forge requires a value for the --etherscan-api-key option even in cases where a valid API key is not required. Just use a placeholder here.

Verification Endpoints

Once you’ve decided where to verify, ensure that you are making your verification request to the correct API endpoint. In Hardhat, this “verification endpoint” is the apiUrl specified in config; in Foundry, this is the --verifier-url you’ll need to provide in your forge command:

blastscan
Testnet	https://api-sepolia.blastscan.io/api
Mainnet	https://api.blastscan.io/api

blastexplorer
Testnet	https://api.routescan.io/v2/network/testnet/evm/168587773/etherscan
Mainnet	https://api.routescan.io/v2/network/mainnet/evm/81457/etherscan

Verification Examples

Foundry

Use these examples, filling in appropriate values as discussed above, to verify your contracts during deployment using forge script or to verify an existing deployment with forge verify-contract.

Verify During Deployment

forge script <deploy-script> 
    --verify --verifier-url <verification-endpoint> \
    --etherscan-api-key <api-key> --rpc-url <rpc-url> \
    --verify --broadcast -vvvv

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Hardhat

Whether using hardhat-ignition-ethers or hardhat-verify, successful verification in Hardhat is primarily a matter of setting up your hardhat.config.ts or hardhat.config.js file correctly.

You’ll need to configure the networks and etherscan properties as demonstrated below. In order to specify the correct verification endpoint from the table above, you will also need to configure the etherscan.customChains property.

Config

hardhat.config.ts

import { HardhatUserConfig } from "hardhat/config";
import "@nomicfoundation/hardhat-toolbox";
import "@nomicfoundation/hardhat-ignition-ethers";
import { vars } from "hardhat/config";

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

const config: HardhatUserConfig = {
  solidity: "0.8.24",
  networks: {
    "blast-sepolia": {
    url: "https://sepolia.blast.io",
    accounts: [PRIVATE_KEY]
    },
    "blast-mainnet": {
        url: "https://rpc.blast.io",
        accounts: [PRIVATE_KEY]
    },    
  },
  etherscan: {
    apiKey: API_KEY,
    customChains: [
      {
        network: "blast-sepolia",
        chainId: 168587773,
        urls: {
          apiURL: <verification-endpoint>,
          browserURL: <explorer-url>
        }        
      },
      {
        network: "blast-mainnet",
        chainId: 81457,                        
        urls: {
          apiURL: <verification-endpoint>,
          browserURL: <explorer-url>
        }
      }
    ],
    enabled: true
  }
};

export default config;