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Create Your Own ERC-20 Token (2025) [Block Explorer - YouTube tutorial]

Simple ERC-20 (fixed supply + Permit) using Hardhat + TypeScript.

1) Prerequisites

nvm install 22
nvm use 22
node -v
npm -v
  • Git and VS Code (recommended)

2) Clone the starter repo

git clone https://github.com/jspruance/erc20-token-2025.git
cd erc20-token

If you’re following the video, this repo contains a token_complete/ folder you’ll copy files from later.

3) Initialize Hardhat

cd token_build
npx hardhat --init

4) Go through the Hardhat prompts

  • Choose TypeScript template
  • Choose Ethers / TypeScript tooling (if asked)
  • Yes to install recommended dependencies

5) Install app dependencies

npm install @openzeppelin/contracts
npm install dotenv

6) Create .env (project root)

SEPOLIA_RPC_URL=
PRIVATE_KEY=
ETHERSCAN_API_KEY=

Notes

  • Use a throwaway dev wallet (testnet only).
  • Keep the 0x prefix on PRIVATE_KEY.
  • Never commit .env (Hardhat template usually git-ignores it—double-check).

7) Copy in the example files (from token_complete/)

Copy these into your Hardhat project:

  • contracts/MyToken.sol
  • test/MyToken.ts
  • scripts/deploy.ts
  • hardhat.config.ts (replace your generated one)

Replace 'MyToken' and 'MTK' with your token name and ticker symbol.

8) Run tests

npx hardhat test

You don’t need to compile first—hardhat test compiles automatically. (Optional: npx hardhat compile to check build only.)

9) Deploy (Sepolia)

npx hardhat run scripts/deploy.ts --network sepolia

Copy the deployed address from the console output.

10) Verify on Etherscan (optional)

# Pass the exact constructor arg (1,000,000 * 10^18 in this example)
npx hardhat verify --network sepolia <DEPLOYED_ADDRESS> 1000000000000000000000000

What you get

  • MyToken.sol: ERC-20 with fixed supply + ERC20Permit (EIP-2612).
  • Test: Verifies the deployer receives the entire initial supply.
  • Deploy script: Ethers v6 style (waitForDeployment, getAddress).

Troubleshooting

  • INSUFFICIENT_FUNDS on deploy → get Sepolia ETH from a faucet.
  • No account provided / bad key → ensure PRIVATE_KEY in .env includes the 0x prefix.
  • RPC errors → verify SEPOLIA_RPC_URL is a valid HTTPS endpoint (Alchemy/Infura/etc.) and that Sepolia is enabled in your provider project.
  • Verify fails → constructor arg must match exactly; ensure Solidity version & optimizer settings in hardhat.config.ts match your contract. Try again after ~30–60s.

Optional npm scripts

Add to package.json:

{
  "scripts": {
    "build": "hardhat compile",
    "test": "hardhat test",
    "deploy:sepolia": "hardhat run scripts/deploy.ts --network sepolia",
    "verify:sepolia": "hardhat verify --network sepolia"
  }
}

Usage:

npm run deploy:sepolia
npm run verify:sepolia -- <DEPLOYED_ADDRESS> 1000000000000000000000000

🚀 Production Deployment

Once you’re comfortable on Sepolia, you can deploy to Ethereum mainnet (or another L1/L2).

1) Fund your deployer wallet

  • Ensure enough ETH for gas.

2) Update .env

MAINNET_RPC_URL=https://mainnet.infura.io/v3/YOUR_KEY   # or Alchemy/QuickNode
PRIVATE_KEY=0xYOUR_MAINNET_PRIVATE_KEY
ETHERSCAN_API_KEY=YOUR_ETHERSCAN_KEY

3) Add network to hardhat.config.ts

networks: {
  sepolia: { /* ... */ },
  mainnet: {
    url: process.env.MAINNET_RPC_URL || "",
    chainId: 1,
    accounts: process.env.PRIVATE_KEY ? [process.env.PRIVATE_KEY] : [],
  },
},

4) Deploy to mainnet

npx hardhat run scripts/deploy.ts --network mainnet

5) Verify on Etherscan

npx hardhat verify --network mainnet <DEPLOYED_ADDRESS> 1000000000000000000000000

Production tips

  • Triple-check constructor args; supply/config are immutable once live.
  • Gas can spike—deploy during low-fee windows.
  • Consider a security review if this token will hold value.
  • Everything on mainnet is permanent and public.