Video: Develop an ERC20 Crypto Currency - Creating an ERC20 - Advanced Foundry

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Building your own cryptocurrency might sound like a futuristic dream, but with Ethereum’s ERC20 standard and modern development tools like Foundry, it's not only possible—it's practical. This guide walks you through the step-by-step process of creating an ERC20 token from scratch using Foundry, a powerful Ethereum smart contract development toolkit. Whether you're aiming to launch a stablecoin, build a DeFi protocol, or deepen your understanding of blockchain mechanics, mastering ERC20 development is a foundational skill in Web3.

Understanding ERC20 and the Ethereum Token Standard

Before writing code, it's essential to understand what ERC20 is and why it matters. ERC stands for Ethereum Request for Comment, and ERC20 is one of the most widely adopted token standards on the Ethereum blockchain. It defines a set of rules and functions that a fungible token contract must implement to ensure compatibility across wallets, exchanges, and decentralized applications.

Key functions required by the ERC20 standard include:

These functions ensure interoperability and predictability—critical for integration into DeFi ecosystems.

👉 Discover how blockchain developers are shaping the future of finance with token innovation.

Setting Up Your Development Environment with Foundry

Foundry is a blazing-fast, Rust-based framework for Ethereum smart contract development that includes tools for testing, deploying, and debugging. Unlike older frameworks that rely on JavaScript, Foundry uses Solidity for tests, enabling faster execution and closer-to-production environments.

Step 1: Install Foundry

Run the following command in your terminal:

curl -L https://foundry.paradigm.xyz | bash

Then launch foundryup to install the latest binaries.

Step 2: Initialize a New Project

forge init erc20-token
cd erc20-token

This sets up a standard project structure with src/, test/, and script/ directories.

Step 3: Write Your First ERC20 Contract

Create a file src/MyToken.sol:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

contract MyToken {
    string public name = "MyToken";
    string public symbol = "MTK";
    uint8 public decimals = 18;
    uint256 public totalSupply;

    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    constructor(uint256 initialSupply) {
        totalSupply = initialSupply * 10 ** decimals;
        balanceOf[msg.sender] = totalSupply;
        emit Transfer(address(0), msg.sender, totalSupply);
    }

    function transfer(address to, uint256 value) public returns (bool) {
        require(balanceOf[msg.sender] >= value, "Insufficient balance");
        balanceOf[msg.sender] -= value;
        balanceOf[to] += value;
        emit Transfer(msg.sender, to, value);
        return true;
    }

    function approve(address spender, uint256 value) public returns (bool) {
        allowance[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }

    function transferFrom(address from, address to, uint256 value) public returns (bool) {
        require(balanceOf[from] >= value, "Insufficient balance");
        require(allowance[from][msg.sender] >= value, "Allowance exceeded");
        balanceOf[from] -= value;
        balanceOf[to] += value;
        allowance[from][msg.sender] -= value;
        emit Transfer(from, to, value);
        return true;
    }
}

This minimal implementation adheres to the EIP-20 specification and allows core token functionality.

Testing Your ERC20 Token with Foundry

One of Foundry’s standout features is its ability to write tests in Solidity. This improves speed and reduces context switching.

Create a test file test/MyToken.t.sol:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

import "forge-std/Test.sol";
import "../src/MyToken.sol";

contract MyTokenTest is Test {
    MyToken token;

    function setUp() public {
        token = new MyToken(1000);
    }

    function testInitialSupply() public {
        assertEq(token.totalSupply(), 1000 * 10 ** 18);
    }

    function testTransfer() public {
        token.transfer(address(1), 100);
        assertEq(token.balanceOf(address(1)), 100 * 10 ** 18);
    }

    function testApproveAndTransferFrom() public {
        token.approve(address(this), 50);
        token.transferFrom(msg.sender, address(2), 50);
        assertEq(token.balanceOf(address(2)), 50 * 10 ** 18);
    }
}

Run tests using:

forge test -vv

Foundry compiles and executes tests instantly, providing immediate feedback.

👉 See how real-world developers use advanced tooling to build secure blockchain applications.

Deploying Your Token Using a Foundry Script

To deploy your token to a local or live network, create a deployment script in script/Deploy.s.sol:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

import "forge-std/Script.sol";
import "../src/MyToken.sol";

contract DeployScript is Script {
    function run() public {
        vm.startBroadcast();
        new MyToken(1000);
        vm.stopBroadcast();
    }
}

Deploy to a local Anvil node:

anvil
forge script script/Deploy.s.sol --rpc-url http://localhost:8545 --broadcast

You can also use a Makefile to simplify these commands and streamline your workflow.

Enhancing Security with OpenZeppelin

While building from scratch teaches core concepts, production-grade tokens should leverage battle-tested libraries like OpenZeppelin. It provides secure implementations of ERC20 with additional features like pausability, minting, and role-based access control.

Install OpenZeppelin:

forge install OpenZeppelin/openzeppelin-contracts

Update your contract:

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

contract MySecureToken is ERC20 {
    constructor() ERC20("MySecureToken", "MST") {
        _mint(msg.sender, 1000 * 10 ** decimals());
    }
}

This approach reduces vulnerabilities and accelerates development.

FAQ: Frequently Asked Questions About ERC20 Development

Q: What is the difference between ERC20 and BEP20?
A: ERC20 is the Ethereum-based token standard, while BEP20 is used on Binance Smart Chain. Both are functionally similar but operate on different blockchains.

Q: Can I change the total supply after deployment?
A: Only if your contract includes a minting function. Otherwise, the supply is fixed once deployed.

Q: Is it safe to build an ERC20 token from scratch?
A: For learning purposes, yes. But for production, always use audited libraries like OpenZeppelin to avoid costly vulnerabilities.

Q: How do I add decimals to my token?
A: Set the decimals variable (commonly 18). This defines how many digits appear after the decimal point in wallet displays.

Q: Can I deploy my token on multiple blockchains?
A: Yes—after testing on Ethereum, you can deploy on EVM-compatible chains like Polygon, Arbitrum, or BSC using the same codebase.

Q: What tools help audit my ERC20 contract?
A: Use Slither or MythX for automated security analysis. Foundry’s testing suite also helps catch logic errors early.

👉 Explore how developers use secure frameworks to prevent smart contract exploits.

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By mastering ERC20 creation with Foundry, you're not just building a token—you're gaining deep insight into how decentralized systems operate at the code level. Whether you're pursuing a career as a Web3 developer or Smart Contract Engineer, these skills open doors to high-impact roles in the rapidly evolving blockchain space.