Proof of work
Also called: Proof of Work, PoW
Proof of work requires miners to spend computing power to validate a block. This real cost is what secures the blockchain.
Proof of work, or PoW, is the method Bitcoin and many other cryptocurrencies use to agree on the history of transactions without any central authority. To add a block, a miner has to present a hash that meets the target set by the difficulty. The only way to find one is to try a staggering number of combinations.
The principle relies on an asymmetry: finding the solution costs a lot of energy and hardware, but checking it takes any node on the network just an instant. To rewrite history, an attacker would need more computing power than all the honest miners combined. It is this very real expense that protects the network, and it is what the block reward compensates.
Only proof-of-work coins can be mined with ASICs or graphics cards. Bitcoin, Litecoin, Dogecoin, Kaspa and Ethereum Classic are among them. Ethereum, on the other hand, switched to proof of stake in September 2022: since then it can no longer be mined, and GPU mining of Ethereum has disappeared. Before buying anything, check that the coin you are targeting really runs on proof of work.
Our page comparing ASICs and graphics cards helps you choose the right hardware for the coin you have in mind.