Hash rate

Hash rate is the total computing power being used to mine a proof-of-work blockchain, measured in hashes per second. Bitcoin's hash rate is so large that it is quoted in exahashes per second (EH/s), where one exahash is a quintillion (10^18) hashes.

Nobody reports their hash rate directly. It is estimated from how quickly blocks are being found relative to the current difficulty, so daily figures are noisy and are usually smoothed over several days.

A higher hash rate makes a 51% attack more expensive, because an attacker would need to control more computing power than the rest of the network combined. Hash rate also reflects miner economics: it tends to rise when the coin's price rises or electricity gets cheaper, and can drop sharply when mining becomes unprofitable, such as just after a halving or when a region bans mining.