Mining

Mining is the process of using computing power to validate transactions and add new blocks to a proof-of-work blockchain, earning newly issued coins and transaction fees in return. Miners repeatedly run a hashing function over a candidate block, changing a small input each time, until they find a result below a network-defined target. The first miner to find a valid result broadcasts the block, and the network accepts it if it follows the rules.

On Bitcoin, for example, specialized machines compute the SHA-256 hash function trillions of times per second competing for the block reward. When a miner wins, the block they assembled — containing recent transactions from the mempool — becomes part of the permanent chain, and every other miner moves on to building the next block on top of it.

A common misconception is that mining involves solving useful math problems; in reality it is deliberately wasteful guesswork, and that expense is the point — it makes rewriting history prohibitively costly. Mining serves two roles at once: it distributes new coins without a central issuer, and it secures the ledger, because an attacker would need to outspend the combined honest mining power to reverse confirmed transactions. Not all blockchains use mining; proof-of-stake networks like Ethereum replaced it with validators who lock up coins instead of burning electricity.