What is mining?

Mining is the process that secures proof-of-work blockchains. On Bitcoin and a small number of other networks, transactions are bundled into blocks, and miners compete to add the next block by solving a computational puzzle. The winner gets paid in freshly issued coins plus transaction fees, and everyone else's work for that round is discarded. It is a wasteful-looking design that, under the hood, turns electricity into security.

The puzzle

Every block has a header that includes the previous block's hash, a Merkle root summarizing the block's transactions, a timestamp, and a random number called a nonce. Miners hash this header with SHA-256 and check whether the result, interpreted as a number, is below a target set by the network. If yes, the miner found a valid block. If no — which is overwhelmingly likely — they bump the nonce and try again.

The target is the "difficulty" of the chain. Bitcoin recalibrates it every 2,016 blocks (about two weeks) so that, given total hashing power, blocks arrive on average every ten minutes. If more miners join, difficulty rises; if miners leave, it falls. This feedback loop keeps the issuance schedule predictable regardless of how much hardware is pointed at the problem.

There is no shortcut. The only way to find a valid hash is to try, and the only resources that help are faster hardware and more of it.

Hardware and electricity

Bitcoin mining ran on CPUs in 2009, GPUs in 2010–2011, FPGAs briefly, and since 2013 has been dominated by ASICs — chips that do nothing but SHA-256 hashes, at extraordinary rates. A modern ASIC does on the order of two hundred trillion hashes per second. A warehouse of them does hundreds of quadrillions.

This arms race is why mining evolved from a hobby into an industrial business. Profitability depends on three things: the Bitcoin price, the network's total hash rate (your share of rewards), and the price of electricity. Marginal operators run on stranded hydro, flare gas, curtailed wind, and whatever power is cheapest and least demanded by other users.

The energy consumption is real. Bitcoin uses more electricity than many small countries. Whether that is wasteful depends on what you think security is worth and where the electricity comes from. Proponents argue that miners are uniquely location-flexible demand that can monetize otherwise-stranded energy and stabilize grids. Critics argue that any electricity spent on mining could have gone to something else.

Pools, rewards, and the halving

Individual miners almost never solo-mine anymore. The variance is punishing: a single ASIC might win a block once every several years by luck. Instead, miners join a pool — Foundry, AntPool, F2Pool, ViaBTC — which aggregates hash rate, wins blocks regularly, and pays out rewards in proportion to contributed work. Pool fees are typically one to two percent.

The block reward in Bitcoin halves roughly every four years. It was 50 BTC at launch, 25 after the 2012 halving, and by 2024 it had dropped to 3.125 BTC per block. Eventually new issuance stops entirely — the 21-millionth coin will be mined around 2140 — and miners will be paid purely from transaction fees. How that transition plays out is one of the open questions of Bitcoin's long-term security model. See the halvings explainer.

Why proof-of-work works

The security argument is blunt. To rewrite Bitcoin history, an attacker would need to produce an alternate chain longer than the current one, which means redoing all the hashing work faster than the rest of the network. That cost scales with total mining power. As long as honest miners outpace any attacker, the chain is safe.

The tradeoff is physical. Ethereum abandoned proof-of-work in 2022 for proof-of-stake (see the comparison explainer), citing energy use and scalability. Bitcoin's community sees the energy expenditure as a feature, not a bug: the security of the network is backed by real-world resources that cannot be spoofed.

Why it matters

Mining is where the abstract idea of a blockchain meets the physical world. Every Bitcoin in circulation exists because somebody, somewhere, ran hardware that burned electricity to find a hash. It is the part of the system that is slowest to change, most expensive to attack, and most central to why Bitcoin is taken seriously as a settlement network. You do not need to mine to use Bitcoin, but understanding how mining works is how you understand what "decentralized" actually costs.