What is a blockchain?
A blockchain is a shared digital ledger maintained across many computers. Records are grouped into blocks and linked in order, which makes past entries extremely hard to change.
The structure
Transactions are bundled into blocks. Each block is cryptographically linked to the previous one, forming a chain. Because changing an old block would break every block after it, the history becomes tamper-evident.
Why it's 'shared'
Many independent computers each keep a full copy and check new blocks against the rules. Agreement among them — not a central authority — is what makes the record trustworthy.
Blockchain is the foundation under crypto, stablecoins, and many payment ideas. Understanding it demystifies almost everything built on top.
Imagine a chain of sealed boxes where each box's lid is stamped with a summary of the box before it. Tampering with one box changes every stamp after it — instantly visible to everyone.
- 'Recorded forever' means mistakes are usually permanent.
- Not everything called 'blockchain' is decentralized or secure — the word alone guarantees nothing.
- Public ledgers are transparent; activity can sometimes be traced.
See the ecosystem map
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Last reviewed 2026-06-25. This topic can change over time; always confirm current specifics from primary sources.