What is Proof of work?
A consensus system where miners expend real energy to win the right to add blocks — making history expensive to rewrite. Bitcoin's model, and the source of its energy debate.
Proof of work is Bitcoin's security engine: miners burn real energy racing to solve puzzles, the winner adds the next block, and rewriting history would mean redoing that work faster than the entire honest network combined. The expense isn't a flaw in the design — it is the design. Forgery is prevented by making it cost more than it could ever pay.
The energy debate follows directly and honestly has two sides: critics point at country-scale electricity consumption for a payments ledger; defenders note that the cost is the security, that mining chases the world's cheapest (often stranded or renewable) power, and that securing hundreds of billions in value isn't free in any system — banks have skyscrapers and armies of auditors. Ethereum's 2022 exit to proof of stake made Bitcoin PoW's defining specimen; whether that conservatism is prudence or stagnation is the multi-decade experiment we're all watching.
See it in practice
Related terms: Mining · Proof of stake · Bitcoin · full glossary
FAQ
Why does Bitcoin use so much energy?
Deliberately — the energy expenditure is what makes attacking or rewriting the ledger economically irrational. The honest debate isn't whether it uses much (it does) but whether censorship-resistant money is worth its security budget.
Could Bitcoin switch to proof of stake like Ethereum?
Technically conceivable, socially near-impossible — Bitcoin's culture treats PoW as constitutive, and its governance makes contentious changes extraordinarily hard. Plan around Bitcoin staying PoW indefinitely.
General information only, not financial advice. Definitions are maintained in our fact database and reviewed with the daily rebuild.