Average number of shielded actions (Sapling spends + outputs, Orchard actions, Ironwood actions, JoinSplits) per shielded transaction. Higher density indicates more complex shielded operations — multi-output sends, consolidations, or mixing-like behavior.
Shielded actions per shielded transaction. One action is roughly one note being spent or created, so a simple payment is a couple and a consolidation sweeping many notes is many. Rising density means transactions are doing more work each, not that there are more of them — for that see transactions per day.
It is a privacy signal only indirectly. More actions per transaction makes an individual payment harder to pick apart, but a wallet consolidating its own notes raises this number without anyone gaining privacy. Read a rise as “heavier transactions” and check the anonymity set before reading it as anything more.
The unit is not identical across pools — Sapling counts spends plus outputs where Orchard counts one action per spend-output pair, the same asymmetry described on activity per ZEC. It also drives the fee a transaction pays: the rule that sets fees (ZIP-317, a Zcash Improvement Proposal) prices by action.