By the end you’ll have written a chain in 200 lines, held your own keys, and sent a transaction you can look up on a public explorer.
You’ve read the explainers and you still can’t say what a blockchain does when nobody is watching. Prices, memes, and hand-waving diagrams don’t tell you where the money actually lives or who decides your transaction happened. This course fixes that by making you build the thing. You start by hashing strings by hand and watching one changed character break a whole chain. You write a small chain in about 200 lines — blocks, mining, a mempool, two nodes disagreeing — with no libraries. Then you generate a private key, derive a public key and an address from it, and see why a seed phrase is the whole account. You install MetaMask, claim free test ether from a faucet on the Sepolia test network, and send a transaction you can look up yourself. You read the two standards behind most tokens and digital collectibles — ERC-20 for interchangeable units, ERC-721 for one-of-a-kind ones — as code, not marketing. You deploy a first Solidity contract. You finish on custody: phishing, approval attacks, multi-signature wallets, and a checklist you’ll actually keep. Everything runs on test networks, so it costs nothing.
Built by Lakshya Kumar
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Two small tools carry every chain: a fingerprint that catches any edit, and a signature that proves you sent it without exposing your key.
Write blocks, mining, a mempool, and a fork-resolution rule yourself, and the whole design stops feeling like magic.
Derive a public key and an address from a private key by hand, and you’ll see why a seed phrase is the entire account.
Learn the plumbing you touch on every transaction: which network you’re on, which node answers you, and what gas is actually paying for.
Proof-of-work and proof-of-stake side by side, plus the honest answer on finality, 51% attacks, and why Ethereum switched.
Install a wallet, claim free test ether, and send a transfer you can watch confirm on a public explorer — for zero dollars.
Read the token standards as code and learn why a one-line approval is the most dangerous thing you’ll ever sign.
Write Solidity from storage to events, deploy it to a test network, and meet the reentrancy bug that has drained real money.
Audit your own setup against a real checklist — phishing, approval attacks, and hot-versus-cold storage — before real money is on it.
Complete all modules, then submit the required number of capstone projects. Each must earn a passing rating from an admin reviewer.
Write a minimal Solidity contract (counter, guestbook, or tiny token), deploy to a public testnet, and verify it on the block explorer.
Paste this into any AI chat. Fill in the bracketed parts with your context — you'll get back a straight answer on whether this belongs on your plate.
I'm considering a "Blockchain 101" course that covers: hashing, signatures, building a toy chain in code, wallets and private keys, how Ethereum accounts and gas work, sending a real testnet transaction, writing your first Solidity contract, and basic custody/security. Here's my situation: 1. My background is: [e.g. "backend engineer", "product manager", "student", "curious but non-technical"] 2. The reason I'm even looking at blockchain is: [e.g. "friends invested and I feel dumb", "my company is exploring stablecoins", "I want to build something", "I just want to understand the news"] 3. I've already tried to learn about blockchain by: [e.g. "reading one article", "nothing", "I've bought crypto but don't understand it"] Answer these directly: - Is "learning how blockchains actually work" likely to help someone in my situation, or is it a dead end? Be blunt. - Name 2 real use-cases in my life or field where understanding the mechanics (not just the price) would matter. - If I finish this course, what could I realistically build or do in 30 days that I can't do today? - What's one reason someone like me might regret spending 25 hours on this? I want to hear the downside, not a pitch.
Free online. Deeper and slower than this course — great companion once you finish Module 5.