PoWSOURCE-LED ANSWER
How does Bitcoin proof of work work?
Understand hashes, mining difficulty and what proof of work can—and cannot—decide in Bitcoin.
Proof of work is a costly lottery for ordering valid blocks. Miners repeatedly hash candidate block headers until one falls below the current target. Nodes can verify the result cheaply, but they still reject any block that violates Bitcoin’s consensus rules.
Mining searches; it does not solve a useful equation
SHA-256 turns a block header into an unpredictable hash. Miners vary the nonce and other header inputs, trying again at enormous scale. A lower target makes a qualifying result rarer and therefore more expensive to find.
Difficulty keeps time approximately stable
Every 2,016 blocks, nodes adjust the target from the time taken by the previous period. More hashrate therefore does not permanently accelerate issuance; it mainly raises the work required to win the next blocks.
Work orders valid history, nodes enforce validity
The chain with the most accumulated work gives nodes an objective way to choose between competing valid histories. It does not let miners create extra coins, spend without signatures or ignore other consensus rules.
Proof of work does not prove that every transaction is honest or lawful. It proves that measurable computation was spent on a candidate history; full validation answers whether that history obeys the protocol.