Understanding how the blockchain works

Blockchain is far more than cryptocurrency. It’s the technology underlying Bitcoin and every other crypto asset, and it’s now applied to everything from supply chain tracking to settling crypto ETFs. This guide gives a plain-English overview of how it works.

What is a blockchain? #

A blockchain is a decentralised ledger — a shared record-keeping system that lets people securely store and transfer information and value without a central operator. The name describes the structure: data is saved in “blocks”, and each new block is cryptographically linked to the last, forming a permanent “chain”. Each block carries a timestamp, and every time a block is added on top, the blocks beneath it become progressively harder to alter. The whole record is visible to anyone on the network.

Because it’s decentralised, the ledger isn’t stored on one computer or supervised by one company, organisation or bank. It’s distributed across every computer participating in the network. If you’ve used a shared online document that updates in real time for multiple people, you have a rough sense of the model — except a blockchain is append-only: history can’t be edited.

The basic elements #

• The record — any information the network tracks (in crypto: who sent what to whom)
• The block — a batch of records bundled together
• The chain — every block, linked in order back to the first

A transaction, step by step #

All blockchain transactions, whatever the network, follow the same pattern:

1. A transaction is created and signed. The sender signs it with their private key, which proves ownership without revealing the key.
2. The network validates it. Connected computers (nodes) check the transaction is genuine — right signatures, sufficient funds, correct format. This verification happens across many nodes, not one authority.
3. Verified transactions are bundled into a block. Each block gets a unique code called a hash — a fingerprint of the block and everything in it. Every block also stores the hash of the block before it, which is what chains them together and fixes their chronological order.
4. The block is added and copied everywhere. Once the network reaches agreement (consensus), the block joins the chain and every node updates its copy of the ledger. How often that happens depends on the network: roughly every ten minutes on Bitcoin, about every twelve seconds on Ethereum.

Because each block embeds the previous block’s hash, changing anything in an old block would change its hash — and every subsequent block would then flag the mismatch. That’s the core of blockchain’s tamper resistance. Our blockchain architecture guide goes deeper into hashing, consensus and node types for readers who want the detail.

Smart contracts and beyond #

Blockchains can do more than record transfers. Smart contracts are programs stored on the blockchain that execute automatically when their conditions are met — paying out an insurance claim when a flight is delayed, releasing escrow funds on delivery, or running an entire decentralised exchange. Ethereum pioneered this and most blockchains now support it, which is how applications from lending protocols to staking operate without a company in the middle.

Blockchains also offer a distinctive approach to data verification: a network can confirm that a transaction is valid without needing to know the identity of the person making it. That combination — verifiable facts, minimal personal data — is increasingly relevant as privacy regulation tightens.

Why it matters #

A blockchain is decentralised and effectively immutable. For industries where security, transparency, auditability and cost matter — finance, logistics, insurance, record-keeping — that’s a genuinely different tool from a conventional database, not just a trendy one. And for cryptocurrency specifically, it’s the reason you can send value to anyone in the world and trust that it arrived, without asking anyone’s permission.

If that’s convinced you to try it yourself, start with our step-by-step guide to buying Bitcoin in Australia.

FAQ #

Is a blockchain the same as a database? No. Databases are editable and controlled by an administrator; blockchains are append-only and maintained by distributed consensus. For most business uses a database is still the better tool — blockchains shine when multiple parties who don’t trust each other need one shared record.

Who controls a blockchain? No one, and everyone. The majority of network participants — miners (who secure the chain with computing power) or stakers (who secure it with coins they’ve pledged), plus the full nodes keeping the ledger — collectively decide what’s valid. This is also a key security feature.

What happens if I send crypto to the wrong address? The transaction is valid, so the network processes it — and it’s irreversible. Always verify addresses carefully.