Cluster pays awards wins for groups of identical symbols that touch each other horizontally or vertically, wherever they sit on the grid. There are no paylines; the size of the cluster sets the prize.
Each game sets a minimum cluster size, often five, and bigger clusters pay more. Diagonal contact usually does not count. Cluster games are normally grid slots with more positions than a standard 5x3 layout, and they almost always use cascading reels, so winning clusters vanish and new symbols drop in, sometimes forming fresh clusters.
The mechanic tends to produce chains of small wins with occasional large ones when a cascade sequence builds, often with a multiplier attached. It does not change the published RTP. See our cluster pays feature page.