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Hemapriya Kanagala
Hemapriya Kanagala

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How I Built a Blockchain User Profile with Solidity (and You Can Too)

#web3 #solidity #ethereum #beginners

This is a smart contract I wrote using Solidity that lets people register and update their profile on the blockchain. It was one of the first contracts I built to understand how user data works on Ethereum.

The idea is simple:

Everyone has a wallet address. What if we could let each address store their name, age, and email - all saved on-chain?

So I built that.

Here is the GitHub link if you want to check out the code.

I wrote just one file: UserProfile.sol.

What This Contract Does

This smart contract lets a user:

  • Register their name, age, and email
  • Update that information later
  • View their own profile (no one else can access it)

Everything is connected to their Ethereum wallet address, so you don’t need to log in - your wallet is your ID.

Concepts I Used

If you're new to Solidity or smart contracts, these are the main building blocks I used:

Concept What It Does
struct Groups related data - like name, age, and email - into a single object
mapping Stores info for each user using their wallet address as the key
require() Adds checks so people don’t register twice or update before registering
block.timestamp Saves the time a user registered, using the blockchain’s clock

Each time someone registers, their info is stored on the blockchain - and only they can update or view it.

How It Works

Here’s what the contract does in plain English:

1. register(name, age, email)

This function saves your profile to the blockchain - but only if you haven’t registered before. If you try again, it gives an error.

2. updateProfile(name, age, email)

If you already registered, this lets you change your info anytime.

3. getProfile()

This function shows your current profile - your name, age, email, and the time you first registered. Only you can see it (based on your wallet).

How to Try It Yourself (Beginner-Friendly)

You don’t need a real wallet or ETH to test this. Remix IDE runs everything in your browser using fake ETH.

Steps to Test the User Profile Contract

  1. Go to Remix

    → https://remix.ethereum.org

  2. Create a new file

    → Click “+” → Name it UserProfile.sol

  3. Paste in the contract code

    → You can find it here on GitHub

  4. Compile it

    → Go to the Solidity Compiler tab

    → Make sure version is 0.8.0 or higher

    → Click Compile

  5. Deploy it

    → Go to the Deploy & Run Transactions tab

    → Select Remix VM (Prague) as environment

    → Leave Value as 0

    → Click Deploy

  6. Register yourself

    → Fill in name, age, and email

    → Click register()

    ✅ You’ll see a green checkmark

  7. Check your profile

    → Click getProfile()

    ✅ Your info will appear: name, age, email, and timestamp

  8. Try updating it

    → Enter new name, age, or email

    → Click updateProfile()

    → Then click getProfile() again to see the updated info

What I Learned

Lesson How I Used It
Structs in Solidity Grouped user info like name, age, email
Mappings Stored each user's profile by their address
Access control with msg.sender Made sure only the owner of a profile can update or view it
Blockchain timestamp Recorded when each user registered
Remix testing Quickly deployed and tested without real ETH

Common Mistakes to Avoid

Mistake Why It’s a Problem How I Solved It
Registering twice Contract would overwrite data Used require() to block double registration
Updating before registering User wouldn’t exist in mapping yet Added require() to check registration first
Returning too much data Could make view functions heavy Kept getProfile() simple and clear

Up Next

In the next post, I’ll show you how I built a Vault app where users can deposit and withdraw ETH securely - and how I used Solidity libraries and events for better logic and tracking.

We’ll also test that app step-by-step in Remix.

I’d really appreciate your questions or feedback. Did something confuse you? Let me know. Your insights help shape the next articles.

Also, if there’s a non-Web3 topic you want me to cover (open source, side projects, etc), drop a comment below. If I know it, I’ll write about it. If not, I’ll point you to a good place to begin.

🤝 Stay in Touch

📚 Also, if you’re new to Web3 in general...

I’m writing another beginner-friendly series called “Foundations of Web3: A Beginner’s Journey”. It covers wallets, testnets, transactions, and more - in simple language.

You can check it out here:

👉 Foundations of Web3: A Beginner’s Journey

Thanks for reading!

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