Difficulty Adjustment

Difficulty adjustment is the rule that keeps a proof-of-work blockchain producing blocks at roughly a target interval no matter how much mining power joins or leaves the network. The network measures how long the last stretch of blocks took and retunes the difficulty target: if blocks came too fast the target tightens and hashes must meet a harder threshold, and if they came too slowly it loosens. Bitcoin recalculates every 2,016 blocks, about two weeks, while other chains adjust every block. This self-correcting loop lets an open network with unpredictable participation keep a stable issuance schedule. It also explains why fees and confirmation times can swing between adjustments when hash rate changes suddenly.