Definition
Share difficulty is the lowered target a mining pool sets for an individual miner so it can measure that miner's contribution. Finding an actual Bitcoin block requires a hash below the full network target, an event far too rare for any single device to demonstrate progress. The pool therefore defines a much easier middle-ground target: any hash that beats it counts as a share, proving the miner is genuinely working without having to find a block.
How it scales
Share difficulty is expressed as a multiple of difficulty 1. A share at difficulty 5 represents five times the proof of work of a difficulty-1 share, so it is worth five times as much toward your payout. The pool assigns each worker a target tuned to its hashrate, typically through an automatic vardiff system, so that submissions arrive at a comfortable rate of roughly one every few seconds.
Why it matters to operators
Share difficulty does not change how much you eventually earn; it only changes the size and frequency of the chunks you report. Set too low, a fast miner floods the pool; set too high, a slow miner submits so rarely that hashrate estimates become noisy. This is the same concept as the network's own target, just scaled down to a per-miner mini-version.
The automatic tuning of this value is handled by vardiff, and each qualifying hash is recorded as a share.
In Simple Terms
Share difficulty is the lowered target a mining pool sets for an individual miner so it can measure that miner’s contribution. Finding an actual Bitcoin…