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So you’ve heard the buzz about Arbitrum…
Low gas fees?
Fast transactions?
Ethereum compatibility?
Now you’re ready to build.
Let’s walk you through your first smart contract on Arbitrum — step by step.
? What We’re Building
We’ll build a simple “On-chain Guestbook”.
Users can submit their name and a message.
The data is stored publicly on the blockchain.
It’s like Web3 Twitter, but way cooler.
? Tools We’ll Use
Step 1: Set Up MetaMask for Arbitrum Sepolia
1. Open MetaMask
2. Select the network dropdown
3. Scroll down and activate testnets, choose sepolia
Step 2: Write the Guestbook Smart Contract
1. Open and install the hardhat package(Hardhat is a framework that helps you write smart contract)
2. Smart Contract
3. Getting your RPC and Private Key
Go to to get your RPC link(this is a gateway for web3 application to connect to the blockchain node).
You need your Private Key:
4. Config your Hardhat Config
You need to install dotenv, to hard your private key and RPC API Key
npm install dotenv
5. Write your deployment Code
6. Deployed to TestNet
? What You’ve Learned
How to configure MetaMask for Arbitrum
How to write and deploy a Solidity contract
How to store and read data on-chain
How easy it is to build on Arbitrum
Get the code from my
Low gas fees?
Fast transactions?
Ethereum compatibility?
Now you’re ready to build.
Let’s walk you through your first smart contract on Arbitrum — step by step.
? What We’re Building
We’ll build a simple “On-chain Guestbook”.
Users can submit their name and a message.
The data is stored publicly on the blockchain.
It’s like Web3 Twitter, but way cooler.
? Tools We’ll Use
- Solidity – Smart contract language
- Hardhat – Framework for writing solidity
- MetaMask – Your wallet for signing transactions
- Arbitrum Sepolia Testnet – So you can deploy for free
- TailwindCSS + JS – For the frontend (covered in next post)
Step 1: Set Up MetaMask for Arbitrum Sepolia1. Open MetaMask
2. Select the network dropdown
3. Scroll down and activate testnets, choose sepolia
- Fund your testnet Go to to fund your account
Step 2: Write the Guestbook Smart Contract1. Open and install the hardhat package(Hardhat is a framework that helps you write smart contract)
2. Smart Contract
3. Getting your RPC and Private Key
Go to to get your RPC link(this is a gateway for web3 application to connect to the blockchain node).
You need your Private Key:
- Open your Metamask
- Select the dropdown icon on your right
- Select Account Details
- Click on Show Private Key
- It will request for your password
- You click on the button to reveal your private key
4. Config your Hardhat Config
You need to install dotenv, to hard your private key and RPC API Key
npm install dotenv
5. Write your deployment Code
6. Deployed to TestNet
? What You’ve Learned
How to configure MetaMask for Arbitrum How to write and deploy a Solidity contract How to store and read data on-chain How easy it is to build on ArbitrumGet the code from my