One-sentence answer
Miners assemble candidate blocks and vary data until the block hash meets the difficulty target, attaching a real and verifiable cost to proposing history.It is not solving a useful math puzzle
Miners vary a nonce and other data, hash the block header, and look for a result below the current target. There is no shortcut to predict a winning attempt, while any node can check one quickly.
That asymmetry—hard to produce and easy to verify—is the core of proof of work.
Why competition needs a cost
If proposing history were nearly free, an attacker could cheaply manufacture many conflicting versions. Proof of work makes candidate blocks carry real computation and energy cost.
Nodes compare accumulated work among valid chains, not a simple count of blocks or node votes.
Mining and issuance
A valid block’s coinbase transaction can claim the subsidy and fees, so mining is also how new BTC enters circulation according to the rules. Issuance is an incentive, not mining’s entire purpose.
As the subsidy declines, fees are expected to become a larger relative part of miner revenue.
Three things to remember
- ✓Mining repeatedly tries hashes; it is not solving an externally useful equation.
- ✓Work is difficult to produce and easy for nodes to verify.
- ✓Miner revenue can include both subsidy and fees.
A common follow-up
Does a larger nonce make a block safer?
No. A nonce is only one field miners can vary. Security comes from accumulated work on a valid chain, not the nonce value itself.
Primary sources
Primary sources
These links lead to protocol material, developer documentation, or open-source code—not trading services.