Proof of work is a method a blockchain uses to decide who gets to add the next BlockBlockA batch of transactions added to a blockchain in one go, together with a reference to the block before it.. Participants have to put in real work, computing that costs hardware and electricity, and the solution to a puzzle is the proof of that work. Bitcoin uses proof of work, as do Dogecoin and Litecoin, for example.
How does it work?
The trick is that the puzzle is extremely hard to solve but easy to check. A miner needs an enormous number of attempts to find the right number. Yet any NodeNodeA computer that runs a crypto network's software, keeps a copy of the blockchain and checks that new transactions and blocks follow the rules. can verify the answer with a single calculation.
Think of a combination lock. Trying every combination takes a long time, but as soon as someone tells you the right code, you can see at once whether it opens the lock.
The idea is older than Bitcoin. The Bitcoin WhitepaperWhitepaperA document in which the creators of a cryptocurrency or project describe how it works, what it is for and which rules apply to it. cites Hashcash, a system by Adam Back designed as a defence against email spam.
Why does it matter?
Proof of work makes cheating expensive. To change an old transaction, an attacker would have to redo the work for that block and every block after it, then catch up with the honest miners. That takes more HashrateHashrateThe total number of guesses a network's mining computers make each second, and a measure of how well the network is protected from attack. than everyone else combined.
Proof of work uses a lot of electricity, which is one of the main criticisms of Bitcoin. Supporters reply that the energy is exactly what makes the network secure, and a 2025 University of Cambridge study found that just over half of it came from renewables and nuclear power. Ethereum stopped using proof of work in 2022 and switched to proof of stakeProof of stakeA consensus method where crypto is locked up as a stake for the right to create blocks, and anyone who cheats can lose part of that stake., which uses about 99.95% less energy.
Everything in Myntkaup Learn is written and regularly reviewed by the Myntkaup editorial team. It is for education and is not investment advice. Editorial policy. Updated 18 October 2026.