Glossary

Blockchain

Plain-language definition Crypto glossary

Key takeaways

A blockchain is a shared, append-only digital ledger that records transactions across a distributed network of computers.
Confirmed transactions are bundled into "blocks," each cryptographically linked to the block before it, forming a chain.
Altering an old record would require re-computing every later block on a majority of the network at once, which makes the history tamper-resistant.

Definition

A blockchain is a shared digital record that stores information in linked batches, called blocks, that are added in sequence and secured with cryptography. Once a block is confirmed and joined to the chain, changing it would require rewriting every block after it, which is what makes the record practically tamper-resistant. Copies of the chain are held across many independent computers (nodes), so no single party can rewrite history alone.

Why it matters

Blockchains are the infrastructure that cryptocurrencies run on. Instead of a bank or clearinghouse keeping the master ledger, the network itself keeps and verifies it, following rules everyone can inspect. That is the core trade-off crypto proposes: a shared, verifiable record kept by a distributed network instead of a single trusted institution.

Example

Bitcoin’s blockchain records every transfer of bitcoin since the network launched. Anyone can download a block explorer and verify a transaction independently, without asking Bitcoin’s developers or any exchange for permission. You can see how live network data is presented on our Bitcoin page.

FAQ

Frequently asked questions

What makes a blockchain tamper-resistant?

Each block is cryptographically linked to the one before it, so changing an old record would mean re-computing every block that followed it on a majority of the network at the same time — which is computationally impractical on a large network.

Is a blockchain the same as Bitcoin?

No. Bitcoin is one cryptocurrency that runs on a blockchain, but blockchains are a general technology used by many networks and applications beyond Bitcoin.

What does "append-only" mean?

New data can be added to the ledger, but existing entries cannot be edited or deleted. The record only ever grows forward, which is central to a blockchain's auditability.