Blockchain technology, explained

A guided path through how blockchains actually work, from hashes and signatures to rollups, bridges and zero-knowledge proofs. Each page answers the question first, gives a concrete example, shows its limits and links its sources. Go in order, or jump to what you need.

How to use this path

Pages are tagged Beginner, Intermediate or Advanced. The stages build on each other, but every page stands on its own and explains the terms it uses. This is education, not investment advice: understanding the technology doesn't tell you whether any coin is worth buying.

Before you start

If blockchains are new to you, these come first.

What is a blockchain?The whole idea in six minutes, with a demo.How does cryptocurrency work?What happens from wallet to block.Blockchain demoEdit a block and watch the chain break.

1. The building blocks

The cryptography and data structures everything else rests on.

What is a hash? SHA-256 and Keccak-256 explainedBeginner A cryptographic hash function turns any input, from one letter to a whole film, into a fixed-size fingerprint.Blocks and transactions: what's insideIntermediate A block is a bundle of transactions plus a small header.Public key vs. private keyKeys, addresses and why one stays secret.Digital signatures: ECDSA, Schnorr and TaprootIntermediate A digital signature is a piece of math that proves the holder of a private key approved one exact message, without revealing the key.Blockchain nodes: full, pruned, light and archiveBeginner A node is a computer running a blockchain's software.

2. How the network agrees

How strangers agree on one history, and how the rules change.

Consensus mechanisms: how blockchains agreeIntermediate A consensus mechanism is the set of rules that lets thousands of independent computers agree on the same order of transactions, even when some of them are faulty or dishonest.What is proof of work?Mining, difficulty and the 51% attack.What is proof of stake?Validators, staking and slashing.Forks: soft forks, hard forks and chain splitsIntermediate A fork is a change to a blockchain's rules.

3. Using the network

What you pay, and what happens to your transaction.

What happens when you send crypto?From pressing send to confirmed.How network fees work: gas, EIP-1559 and sat/vBIntermediate Network fees pay for space in a block.How to look up a crypto transactionLook up any transaction yourself.

4. Scaling

Why blockchains are slow and how layer 2s change that.

Scalability and the blockchain trilemmaIntermediate The blockchain trilemma is the observation that a simple blockchain finds it hard to be very scalable, very secure and very decentralized at the same time.Layer 1 vs. layer 2 vs. sidechainsBeginner A layer 1 is a base blockchain with its own security, like Bitcoin or Ethereum.What are layer 2 networks?The beginner's version: Arbitrum, Base and friends.Rollups: optimistic vs. ZK, data availability and blobsAdvanced A rollup runs transactions off Ethereum, then posts them to Ethereum in compressed batches along with a way to prove they're correct.

5. Connecting to the world

Programs, other chains and real-world data.

What is a smart contract?Programs that run on a blockchain.Bridges and interoperability: how they work and why they get hackedIntermediate Blockchains can't see each other, so a bridge moves value between them, usually by locking coins on one chain and minting a matching "wrapped" token on the other.Oracles: getting real-world data onto a blockchainIntermediate An oracle is a service that brings outside information, like the price of ETH or a sports score, onto a blockchain so smart contracts can use it.Permissioned vs. permissionless blockchainsIntermediate A permissionless blockchain, like Bitcoin or Ethereum, lets anyone read it, send transactions and help run it.

6. Advanced

The frontier: privacy, ordering games and programmable wallets.

Zero-knowledge proofs, explained simplyAdvanced A zero-knowledge proof lets you convince someone that a statement is true, such as "I know the password" or "this batch of 5,000 transactions is valid", without revealing anything else.What is MEV? Transaction ordering explainedAdvanced MEV, maximal extractable value, is the profit someone can make by choosing which transactions go into a block and in what order.Account abstraction: ERC-4337, EIP-7702 and smart walletsAdvanced Account abstraction turns an Ethereum wallet from a single private key into a programmable smart account with its own rules: passkey logins, spending limits, recovery by friends, batched actions, and gas paid by someone else or in tokens.

Keep going

Crypto glossaryEvery term in a sentence or two. Cryptocurrency, beyond the hypeThe long read on how it works and what goes wrong. Safety centerScams and mistakes cost far more than any technical flaw.