What is Proof of Work?

Proof of Work ties a block proposal to computational effort. Bitcoin miners search for a block-header hash less than or equal to the protocol’s target.

What does a miner prove?

Finding an acceptable hash can require many attempts, while checking the result is easier. The proof does not establish the miner’s identity or the commercial trustworthiness of a transaction. It makes block production costly.

A party seeking to change earlier records must also compete computationally with the subsequent chain. The Bitcoin developer guide explains the role of accumulated work in selecting a valid chain. Counting blocks alone is insufficient.

Do full nodes and miners perform the same task?

A miner proposes a block. A full node checks its transactions and issuance against its own rules. More powerful hardware cannot make unauthorized BTC issuance valid to those nodes.

Blockchain describes a record structure; Proof of Work is part of a computation-based consensus process. Not every blockchain uses it.

Example

Imagine a simplified model with hash outputs from 0 to 99 and a target of 9 or less. A miner changes the candidate block data and hashes it again: an output of 42 fails, while 7 meets the target. Other nodes can recompute the hash to check the result. These are illustrative numbers, not Bitcoin’s actual hash range, and no fixed number of attempts guarantees success.