Comparator Update Detector
Updated Jan 05, 2026
Alias: CUD
Definition
A Comparator Update Detector is based on the behavior inherent to comparators where they don't notice inventory changes when reading it through a solid block (including an inventory being moved away or put in place, like a composter being moved by a piston). The CUD will then change it's signal once it either receives a block or inventory update. See updateNeighbourForOutputSignal.
Special behaviors
- Brewing stand: Sends a comparator update when consuming fuel, brewing begins, and when brewing progresses. See calls to
BlockEntity.setChanged()inBrewingStandBlockEntity.serverTick() - Detector rail: Sends a comparator update every tick when an entity is colliding with it. See calls to
ServerLevel.updateNeighbourForOutputSignal()inDetectorRailBlock.tick()