How blockchains work

Ledgers, blocks, nodes, mining and the rules that keep a network honest.

18 guides, in reading order

What is a blockchain?A blockchain is a shared digital record of transactions, stored in linked blocks on many computers, with no single company or bank in charge.2 min read
How does a blockchain work, step by step?A blockchain takes a signed transaction, spreads it across a network of computers, checks it, packs it into a block and links that block to the chain.2 min read
What is a ledger, and what does it do?A ledger is a record of who owns what. In crypto, the ledger is shared by thousands of computers instead of being kept by one bank.2 min read
What is a distributed ledger?A distributed ledger is a record of transactions copied across many computers that keep their copies in sync, with no single master copy.2 min read
What is in a block?A block holds a batch of transactions plus a header with a timestamp, a fingerprint of the previous block and the data used to agree on it.2 min read
What is a hash in blockchain?A hash is a fixed-length digital fingerprint of a piece of data. Blockchains use hashes to link blocks together and to make tampering obvious.2 min read
What is a node?A node is a computer that runs a blockchain's software, keeps a copy of the ledger and checks that every transaction and block follows the rules.2 min read
What is a consensus mechanism?A consensus mechanism is the set of rules that lets computers on a blockchain agree on one version of the ledger without a central authority.2 min read
Proof of work vs proof of stakeProof of work secures a blockchain with computing power and electricity. Proof of stake secures it with coins that participants lock up as a deposit.2 min read
What is crypto mining and how does it work?Crypto mining is a competition among computers to add the next block to a blockchain. The winner earns new coins and fees, and the race secures the network.2 min read
What is a validator?A validator is a participant in a proof-of-stake blockchain who locks up coins as a deposit, then checks transactions and helps add new blocks.2 min read
What does decentralized mean in crypto?Decentralized means no single person, company or government controls the network. Records, rules and decisions are spread among many participants.2 min read
Hard fork vs soft forkA soft fork tightens a blockchain's rules while staying compatible with old software. A hard fork breaks compatibility and can split the chain in two.2 min read
Public vs private blockchainsA public blockchain is open for anyone to use and help run. A private blockchain is run by one organization or a group that decides who may take part.2 min read
What is a 51% attack?A 51% attack is when one party controls most of a blockchain's mining power or staked coins and uses it to reverse or block recent transactions.2 min read
What is a layer 2?A layer 2 is a network built on top of a blockchain that processes transactions off the main chain to make them faster and cheaper.2 min read
What is blockchain used for besides crypto?Outside cryptocurrency, blockchains are used for payments and settlement, tokenized assets, supply chain tracking and digital identity, with mixed results.2 min read
How does cryptography secure cryptocurrency?Cryptography secures crypto with key pairs and digital signatures that prove who may spend coins, and with hashes that make records hard to alter.2 min read