Difficulty adjustment

The adjustment period is 2,016 blocks, which at ten minutes per block should take exactly two weeks, that is 1,209,600 seconds. At the close of each period, the network compares the actual time those 2,016 blocks took with the two-week target. If they were faster, difficulty rises; if slower, it falls. The formula recalculates the target by multiplying it by the actual time divided by the target time, and as a safeguard the adjustment is capped at a factor of four per period to prevent extreme jumps.

It guarantees predictable issuance alongside the subsidy. Blocks arriving roughly every ten minutes sustain the halving schedule and the whole monetary policy, and it is what makes proof-of-work robust against sudden swings in hashrate. The target is the numeric threshold the block hash must fall below, and difficulty is its inverse, human-readable representation.

In practice, the adjustment is the technical counterpart to mining. Together with the subsidy that each halving trims it defines the miner's economics, and by keeping the block pace steady it is what makes the halving, set every 210,000 blocks, fall roughly every four years on the real calendar. Without this mechanism, a flood of hashrate would accelerate issuance and break that predictability.