Bitcoin Mining, explained

“Mining” is a bad metaphor that stuck. Miners aren't digging anything up. They're doing the accounting for the entire Bitcoin network — bundling transactions into blocks and competing for the right to add the next one — and getting paid in new bitcoin for the effort.

What a miner actually does

1. Collects pending transactions broadcast by users into a candidate block.
2. Checks them — every transaction is validated against the rules (valid signatures, no double-spends, correct amounts). Invalid transactions are dropped.
3. Competes to seal the block by solving a proof-of-work puzzle: repeatedly hashing the block's contents with a changing number (a “nonce”) until the result falls below a target value. There's no shortcut; it's trial and error, billions of times per second.
4. Broadcasts the winning block to the network. Everyone else checks it in an instant, adds it to their copy of the chain, and starts competing on the next one.

The puzzle is deliberately hard to solve and trivially easy to verify. That asymmetry is the whole game.

Why waste electricity on purpose?

This is the objection everyone raises, and it's worth answering honestly: the energy is the security. Because writing a block costs real money in electricity and hardware, rewriting history costs real money too — you'd have to redo all that work faster than everyone else combined. The cost isn't a bug; it's the thing that makes the ledger expensive to attack. Remove the cost and you remove the protection.

Whether that trade-off is worth it is a genuine debate, and other networks (Ethereum since 2022) chose a different mechanism, proof of stake, to avoid it. Bitcoin has deliberately kept proof of work.

Difficulty: the self-correcting thermostat

Bitcoin aims to produce one block roughly every ten minutes, no matter how much mining power is online. If more miners join and blocks start coming faster, the network automatically makes the puzzle harder. If miners leave and blocks slow down, it gets easier. This difficulty adjustment happens about every two weeks (every 2,016 blocks). It's why Bitcoin's issuance schedule stays predictable even as the hardware behind it has gone from laptop CPUs to warehouse-scale specialized chips.

From CPUs to ASICs

Early on (2009) you could mine on a normal computer. As bitcoin gained value, miners moved to graphics cards, then to ASICs — chips built to do nothing but Bitcoin's hash function, millions of times more efficiently than a general-purpose CPU. Today mining at any meaningful scale means purpose-built machines, cheap electricity, and often mining pools, where many miners combine their power and split rewards proportionally rather than each waiting years to win a block solo.

What miners get paid

Two things, covered in detail on the Block Rewards page:

• The block subsidy — brand-new bitcoin created with each block (currently 3.125 BTC).
• Transaction fees — small amounts users attach to their transactions to be included sooner.

The subsidy shrinks over time and fees are meant to eventually replace it. That transition is one of the most interesting open questions about Bitcoin's long-term economics.