Beginner30 minutes

Getting Started with Smart Contract Development

Go from zero to deployed smart contract in under 30 minutes. This guide walks you through everything you need to start building on Ethereum.

Prerequisites

Basic programming knowledge (any language)
Command line familiarity
Understanding of blockchain basics (take our course)

Install Development Tools

First, let's install the essential tools you'll need for blockchain development.

Install Node.js

Download and install Node.js (v18 or higher) from nodejs.org

Verify installation

node --version
npm --version

Install Git

Download from git-scm.com or use your package manager:

# macOS
brew install git

# Ubuntu/Debian
sudo apt install git

Choose a Framework

For this tutorial, we'll use Hardhat, the most popular Ethereum development framework.

Hardhat

Recommended

JavaScript/TypeScript based, great documentation, large ecosystem of plugins

Foundry

Rust-based, faster compilation, tests written in Solidity

Create a New Project

Terminal

mkdir my-first-contract
cd my-first-contract
npm init -y
npm install --save-dev hardhat
npx hardhat init

Select "Create a JavaScript project" when prompted. This will create a project structure with example contracts and tests.

Write Your First Contract

Replace the contents of contracts/Lock.sol with this simple storage contract:

contracts/SimpleStorage.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

/// @title SimpleStorage
/// @notice A simple contract to store and retrieve a value
contract SimpleStorage {
    uint256 private storedValue;

    /// @notice Emitted when the stored value changes
    event ValueChanged(uint256 newValue);

    /// @notice Store a new value
    /// @param _value The value to store
    function store(uint256 _value) public {
        storedValue = _value;
        emit ValueChanged(_value);
    }

    /// @notice Retrieve the stored value
    /// @return The currently stored value
    function retrieve() public view returns (uint256) {
        return storedValue;
    }
}

Compile the Contract

npx hardhat compile

You should see "Compiled 1 Solidity file successfully". If there are errors, check your Solidity syntax.

Test Your Contract

Create a test file at test/SimpleStorage.js:

test/SimpleStorage.js

const { expect } = require("chai");

describe("SimpleStorage", function () {
  let simpleStorage;

  beforeEach(async function () {
    const SimpleStorage = await ethers.getContractFactory("SimpleStorage");
    simpleStorage = await SimpleStorage.deploy();
  });

  it("Should store and retrieve a value", async function () {
    // Store value 42
    await simpleStorage.store(42);

    // Retrieve and check
    expect(await simpleStorage.retrieve()).to.equal(42);
  });

  it("Should emit ValueChanged event", async function () {
    await expect(simpleStorage.store(100))
      .to.emit(simpleStorage, "ValueChanged")
      .withArgs(100);
  });
});

Run Tests

npx hardhat test

✓ All tests should pass. Testing is crucial—never deploy untested code to mainnet!

Deploy to Testnet

Now let's deploy to Sepolia testnet. First, you'll need:

A wallet with Sepolia ETH (get free ETH from a faucet)
An RPC URL (free from Alchemy or Infura)

Configure Hardhat

Create a .env file (never commit this!):

SEPOLIA_RPC_URL=https://eth-sepolia.g.alchemy.com/v2/YOUR_KEY
PRIVATE_KEY=your_wallet_private_key_here

Update hardhat.config.js:

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

module.exports = {
  solidity: "0.8.20",
  networks: {
    sepolia: {
      url: process.env.SEPOLIA_RPC_URL,
      accounts: [process.env.PRIVATE_KEY]
    }
  }
};

Deploy Script

Create scripts/deploy.js:

async function main() {
  const SimpleStorage = await ethers.getContractFactory("SimpleStorage");
  const simpleStorage = await SimpleStorage.deploy();
  await simpleStorage.waitForDeployment();

  console.log("SimpleStorage deployed to:", await simpleStorage.getAddress());
}

main().catch((error) => {
  console.error(error);
  process.exitCode = 1;
});

Deploy!

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

Congratulations!

You've deployed your first smart contract! View it on Sepolia Etherscan using the contract address from the console output.

Next Steps

Build an ERC-20 Token

Create your own cryptocurrency token

Solidity Best Practices

Write secure, efficient code

Security Vulnerabilities

Learn common attack vectors