Minecraft wiki entry for Command_blocks_and_functions, associated text: Please note that if you want to use the RequiredPlayerRange tag you have to use the MaxNearbyEntities tag as well. The same thing applies to MinSpawnDelay and MaxSpawnDelay. Lastly, note that the y value used in both of those spawner example codes was ~-1, which (assuming the player are not flying) will put the spawner in the surface level of the ground at your feet.