# Hash

> A short fingerprint of any piece of data, produced by a one-way mathematical function.

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Source: What The Block! Dictionary v1.0 (last updated 2026-04-25), browsable at https://wtb.fudfomo.co.

## Definition

A hash is the fixed-length output of a cryptographic function applied to some input. Hashes are easy to compute one way and effectively impossible to reverse.

They are used everywhere in crypto: linking blocks together, addressing data, signing transactions, and producing proofs. Even the smallest change to the input produces a wildly different hash, which is what makes them useful for detecting tampering.

## Related terms

- [Hash Rate](https://business.fudfomo.co/glossary/hash-rate): How much total computing power is securing a proof-of-work network like Bitcoin.
- [Mining](https://business.fudfomo.co/glossary/mining): Using computers to add new transactions to a blockchain and earn newly created coins as a reward.
- [Merkle Tree](https://business.fudfomo.co/glossary/merkle-tree): A way of summarising many pieces of data into a single hash, used to prove a single piece of data is in the set.
- [Blockchain](https://business.fudfomo.co/glossary/blockchain): A shared digital record of transactions that no single person or company controls. Everyone can read it, and changes are extremely hard to fake.

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