What is proof of work? The consensus mechanism that powers bitcoin

Proof of work is a consensus mechanism that forces computers to spend measurable energy solving a mathematical puzzle before they can add a new block of transactions to a blockchain. It is the reason bitcoin has value as a settlement network and the reason that network consumes more electricity than some countries. Summary Proof of work requires miners to find a hash output below a target threshold by repeatedly guessing a nonce value, consuming real computational energy in the process. Bitcoin adjusts its mining difficulty every 2,016 blocks, roughly every two weeks, to maintain an average block time of 10 minutes regardless of how much computing power joins or leaves the network. The global bitcoin network hash rate exceeded 1 exahash per second in mid 2026, meaning miners collectively perform more than one quintillion hash computations every second. Proof of work is not the only consensus mechanism. Proof of stake, used by Ethereum since September 2022, replaces energy expenditure with economic collateral but introduces different security tradeoffs. The environmental debate around proof of work is real but more nuanced than headlines suggest. Roughly 55 to 60 percent of bitcoin ...