Plasma Docs - Build on Plasma

Prerequisites

A deployed contract on Plasma testnet. See deploy a contract if you haven’t deployed one yet.
Your contract’s source code and compilation settings.
Constructor arguments used during deployment (if any).

The Plasma block explorer (plasmascan.to) serves an Etherscan-compatible verification API. The examples below use that API directly — no third-party account is required to submit a verification.

Example Contracts

We’ll use two example contracts to demonstrate both simple and complex constructor arguments:

Simple Contract

A basic data storage contract that demonstrates fundamental smart contract concepts.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.28;

contract SimpleStorage {
    string private storedData;
    address public owner;
    
    constructor(string memory initialData) {
        storedData = initialData;
        owner = msg.sender;
    }
    
    function setData(string memory data) public {
        require(msg.sender == owner, "Only owner can set data");
        storedData = data;
    }
    
    function getData() public view returns (string memory) {
        return storedData;
    }
}

Complex Contract

A more sophisticated vault system for managing token deposits with configurable parameters.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.28;

contract TokenVault {
    struct VaultConfig {
        uint256 minDeposit;
        uint256 maxDeposit;
        bool isActive;
    }
    
    address[] public authorisedTokens;
    VaultConfig public config;
    mapping(address => uint256) public balances;
    
    constructor(
        address[] memory _tokens,
        uint256 _minDeposit,
        uint256 _maxDeposit,
        bool _isActive
    ) {
        authorisedTokens = _tokens;
        config = VaultConfig(_minDeposit, _maxDeposit, _isActive);
    }
    
    function deposit(address token, uint256 amount) external {
        require(config.isActive, "Vault is not active");
        require(amount >= config.minDeposit, "Amount below minimum");
        require(amount <= config.maxDeposit, "Amount above maximum");
        balances[msg.sender] += amount;
    }
}

Verify with Foundry

Foundry provides the forge verify-contract command for contract verification.

Ensure your foundry.toml includes the verification settings:

[profile.default]
src = "src"
out = "out"
libs = ["lib"]
solc_version = "0.8.28"
optimizer = true
optimizer_runs = 200

[rpc_endpoints]
plasma_testnet = "https://testnet-rpc.plasma.to"

Verify the contract. For the SimpleStorage contract with a string constructor argument:

forge verify-contract \
  --chain-id 9746 \
  --num-of-optimizations 200 \
  --watch \
  --constructor-args $(cast abi-encode "constructor(string)" "Hello, Plasma!") \
  --compiler-version v0.8.28+commit.7893614a \
  0x742d35Cc6610C7532C8582d4C371Acb1D5f44D7F \
  src/SimpleStorage.sol:SimpleStorage

For the TokenVault contract with multiple constructor arguments:

# First, encode the constructor arguments.
CONSTRUCTOR_ARGS=$(cast abi-encode \
    "constructor(address[],uint256,uint256,bool)" \
    "[0x1234567890123456789012345678901234567890,0x0987654321098765432109876543210987654321]" \
    1000000000000000000 \
    10000000000000000000 \
    true)

forge verify-contract \
    --chain-id 9746 \
    --num-of-optimizations 200 \
    --watch \
    --constructor-args $CONSTRUCTOR_ARGS \
    --compiler-version v0.8.28+commit.7893614a \
    0x9876543210987654321098765432109876543210 \
    src/TokenVault.sol:TokenVault

Check verification status. Foundry will show real-time verification status with the --watch flag. Look for:

Submitting verification for [src/SimpleStorage.sol:SimpleStorage] 0x742d35Cc6610C7532C8582d4C371Acb1D5f44D7F.
Submitted contract for verification:
        Response: `OK`
        GUID: `abc123def456ghi789`
        URL: https://testnet.plasmascan.to/address/0x742d35Cc6610C7532C8582d4C371Acb1D5f44D7F
Contract verification status:
Response: `NOTOK`
Details: `Pending in queue`
Contract verification status:
Response: `OK`
Details: `Pass - Verified`
Contract successfully verified

Verify with Hardhat

Hardhat offers contract verification through the @nomicfoundation/hardhat-verify plugin.

Update your hardhat.config.js to include verification settings:

require("@nomicfoundation/hardhat-toolbox");
require("@nomicfoundation/hardhat-verify");
require("dotenv").config();

module.exports = {
  solidity: {
    version: "0.8.28",
    settings: {
      optimizer: {
        enabled: true,
        runs: 200
      }
    }
  },
  networks: {
    plasmaTestnet: {
      url: process.env.RPC_URL,
      chainId: 9746,
      accounts: [process.env.PRIVATE_KEY]
    }
  },
  etherscan: {
    customChains: [
      {
        network: "plasmaTestnet",
        chainId: 9746,
        urls: {
          apiURL: "https://testnet.plasmascan.to/api",
          browserURL: "https://testnet.plasmascan.to/"
        }
      }
    ]
  },
  sourcify: {
    enabled: false
  }
};

Verify the contract. For the simple contract:

npx hardhat verify \
    --network plasmaTestnet \
    0x742d35Cc6610C7532C8582d4C371Acb1D5f44D7F \
    "Hello, Plasma!"

For contracts with multiple constructor arguments, create a verification script scripts/verify.js:

const hre = require("hardhat");

async function main() {
  const contractAddress = "0x9876543210987654321098765432109876543210";
  
  // Constructor arguments for TokenVault.
  const constructorArgs = [
    [
      "0x1234567890123456789012345678901234567890",
      "0x0987654321098765432109876543210987654321"
    ], // address[] _tokens
    "1000000000000000000", // uint256 _minDeposit (1e18, assuming 18 decimals)
    "10000000000000000000", // uint256 _maxDeposit (1e19, assuming 18 decimals)
    true // bool _isActive
  ];

  try {
    await hre.run("verify:verify", {
      address: contractAddress,
      constructorArguments: constructorArgs,
    });
    console.log("Contract verified successfully!");
  } catch (error) {
    console.error("Verification failed:", error);
  }
}

main()
  .then(() => process.exit(0))
  .catch((error) => {
    console.error(error);
    process.exit(1);
  });

Run the verification script:

npx hardhat run scripts/verify.js --network plasmaTestnet

Automated Verification During Deployment

You can also verify contracts automatically during deployment by adding verification to your deployment script:

const { ethers } = require("hardhat");

async function main() {
  const SimpleStorage = await ethers.getContractFactory("SimpleStorage");
  const simpleStorage = await SimpleStorage.deploy("Hello, Plasma!");
  
  await simpleStorage.waitForDeployment();
  const contractAddress = await simpleStorage.getAddress();
  
  console.log("SimpleStorage deployed to:", contractAddress);
  
  // Wait for a few block confirmations before verifying.
  console.log("Waiting for block confirmations...");
  await simpleStorage.deploymentTransaction().wait(5);
  
  // Verify the contract.
  try {
    await hre.run("verify:verify", {
      address: contractAddress,
      constructorArguments: ["Hello, Plasma!"],
    });
    console.log("Contract verified successfully!");
  } catch (error) {
    console.log("Verification failed:", error.message);
  }
}

main();

Verify with Ethers.js

Ethers.js requires manual API calls to the block explorer for verification. This approach gives you full control over the verification process.

Install the required dependencies:

npm install ethers dotenv axios form-data

Create verification script verify-ethers.js:

const axios = require('axios');
const fs = require('fs');
require('dotenv').config();

async function verifyContract(contractAddress, sourceCode, contractName, constructorArgs = "") {
  const apiUrl = "https://testnet.plasmascan.to/api";
  
  const data = {
    module: 'contract',
    action: 'verifysourcecode',
    contractaddress: contractAddress,
    sourceCode: sourceCode,
    codeformat: 'solidity-single-file',
    contractname: contractName,
    compilerversion: 'v0.8.28+commit.7893614a',
    optimizationUsed: '1',
    runs: '200',
    constructorArguements: constructorArgs, // Note: API uses this spelling.
    evmversion: 'default',
    licenseType: '3' // MIT License
  };

  try {
    console.log('Submitting contract for verification...');
    const response = await axios.post(apiUrl, new URLSearchParams(data));
    
    if (response.data.status === '1') {
      const guid = response.data.result;
      console.log('Verification submitted successfully!');
      console.log('GUID:', guid);
      
      // Check verification status.
      await checkVerificationStatus(guid);
    } else {
      console.error('Verification submission failed:', response.data.result);
    }
  } catch (error) {
    console.error('Error submitting verification:', error.message);
  }
}

async function checkVerificationStatus(guid) {
  const apiUrl = "https://testnet.plasmascan.to/api";
  const maxAttempts = 30;
  let attempts = 0;

  while (attempts < maxAttempts) {
    try {
      const response = await axios.get(apiUrl, {
        params: {
          module: 'contract',
          action: 'checkverifystatus',
          guid: guid
        }
      });

      const status = response.data.status;
      const result = response.data.result;

      if (status === '1') {
        console.log('✅ Contract verified successfully!');
        console.log('Result:', result);
        break;
      } else if (result.includes('Fail')) {
        console.error('❌ Verification failed:', result);
        break;
      } else {
        console.log('⏳ Verification pending...');
        attempts++;
        
        if (attempts < maxAttempts) {
          await new Promise(resolve => setTimeout(resolve, 10000)); // Wait 10 seconds.
        }
      }
    } catch (error) {
      console.error('Error checking status:', error.message);
      break;
    }
  }

  if (attempts >= maxAttempts) {
    console.log('⚠️ Verification status check timed out. Please check manually.');
  }
}

// Verify SimpleStorage contract.
async function verifySimpleStorage() {
  const contractAddress = "0x742d35Cc6610C7532C8582d4C371Acb1D5f44D7F";
  const sourceCode = fs.readFileSync('SimpleStorage.sol', 'utf8');
  const constructorArgs = "0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000d48656c6c6f2c20506c61736d612100000000000000000000000000000000000000";
  
  await verifyContract(contractAddress, sourceCode, "SimpleStorage", constructorArgs);
}

// Verify TokenVault contract.
async function verifyTokenVault() {
  const contractAddress = "0x9876543210987654321098765432109876543210";
  const sourceCode = fs.readFileSync('TokenVault.sol', 'utf8');
  
  // Complex constructor arguments (ABI encoded).
  const constructorArgs = "0000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000de0b6b3a76400000000000000000000000000000000000000000000000000008ac7230489e8000000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002000000000000000000000000123456789012345678901234567890123456789000000000000000000000000098765432109876543210987654321098765432100";
  
  await verifyContract(contractAddress, sourceCode, "TokenVault", constructorArgs);
}

// Run verification (uncomment the one you need).
verifySimpleStorage();
// verifyTokenVault();

Encode constructor arguments. For complex constructor arguments, you need to ABI encode them. You can use Foundry’s cast tool:

# For SimpleStorage with string argument.
cast abi-encode "constructor(string)" "Hello, Plasma!"

# For TokenVault with complex arguments.
cast abi-encode \
    "constructor(address[],uint256,uint256,bool)" \
    "[0x1234567890123456789012345678901234567890,0x0987654321098765432109876543210987654321]" \
    1000000000000000000 \
    10000000000000000000 \
    true

Finally, run the verification:
node verify-ethers.js

Check Verification Status

After verification, you can check if it was successful:

On Block Explorer

Visit Plasma testnet explorer.
Search for your contract address.
Look for a green checkmark next to “Contract” tab.
Click the “Contract” tab to view the verified source code.

Programmatically

Create a status check script check-verification.js:

const axios = require('axios');
require('dotenv').config();

async function checkIfVerified(contractAddress) {
  const apiUrl = "https://testnet.plasmascan.to/api";
  
  try {
    const response = await axios.get(apiUrl, {
      params: {
        module: 'contract',
        action: 'getsourcecode',
        address: contractAddress,
      }
    });

    const result = response.data.result[0];
    
    if (result.SourceCode && result.SourceCode !== '') {
      console.log('✅ Contract is verified!');
      console.log('Contract Name:', result.ContractName);
      console.log('Compiler Version:', result.CompilerVersion);
      console.log('Optimisation Used:', result.OptimizationUsed);
      return true;
    } else {
      console.log('❌ Contract is not verified');
      return false;
    }
  } catch (error) {
    console.error('Error checking verification status:', error.message);
    return false;
  }
}

// Check your contract.
checkIfVerified("0x742d35Cc6610C7532C8582d4C371Acb1D5f44D7F");

Alternative Methods

While block explorers are the most common verification method, you can also use:

Sourcify

Sourcify provides decentralised contract verification:

# Install Sourcify CLI.
npm install -g @ethereum-sourcify/cli

# Verify contract.
sourcify verify \
    --network 9746 \
    --address 0x742d35Cc6610C7532C8582d4C371Acb1D5f44D7F \
    --files contracts/SimpleStorage.sol

Tenderly

Tenderly offers verification as part of their debugging platform. See their documentation for details.

Contract Flattening

For contracts with imports or libraries, you may need to flatten your contract into a single file before verification. Popular tools include:

For complex projects with external libraries, see the Hardhat verification documentation for advanced configuration options.

Troubleshooting

Constructor Argument Mismatch

Error: Invalid constructor arguments provided

Double-check your constructor arguments match exactly what was used during deployment. Use cast abi-encode to verify encoding.

Compiler Version Mismatch

Error: Compilation failed

Ensure the compiler version in your verification request matches the version used during compilation.

Optimisation Settings Mismatch

Error: Bytecode doesn't match

Verify that optimisation settings (enabled/disabled and runs count) match your compilation settings.

Already Verified

Error: Contract source code already verified

This means verification was successful previously. Check the block explorer to confirm.

Rate Limiting

Error: Rate limit exceeded

Wait a few minutes before retrying. Consider upgrading your API plan if you need higher limits.

Development

Asset Management

Network Configuration

Smart Contracts

Testing and Resources

Verify a Contract

Prerequisites

Example Contracts

Simple Contract

Complex Contract

Verify with Foundry

Verify with Hardhat

Automated Verification During Deployment

Verify with Ethers.js

Check Verification Status

On Block Explorer

Programmatically

Alternative Methods

Sourcify

Tenderly

Contract Flattening

Troubleshooting

Constructor Argument Mismatch

Compiler Version Mismatch

Optimisation Settings Mismatch

Already Verified

Rate Limiting

​Prerequisites

​Example Contracts

​Simple Contract

​Complex Contract

​Verify with Foundry

​Verify with Hardhat

​Automated Verification During Deployment

​Verify with Ethers.js

​Check Verification Status

​On Block Explorer

​Programmatically

​Alternative Methods

​Sourcify

​Tenderly

​Contract Flattening

​Troubleshooting

​Constructor Argument Mismatch

​Compiler Version Mismatch

​Optimisation Settings Mismatch

​Already Verified

​Rate Limiting

Prerequisites

Example Contracts

Simple Contract

Complex Contract

Verify with Foundry

Verify with Hardhat

Automated Verification During Deployment

Verify with Ethers.js

Check Verification Status

On Block Explorer

Programmatically

Alternative Methods

Sourcify

Tenderly

Contract Flattening

Troubleshooting

Constructor Argument Mismatch

Compiler Version Mismatch

Optimisation Settings Mismatch

Already Verified

Rate Limiting