Storage

The storage tooltip tutorial as seen in game.

The storage is a building that buffers items. Items that match the current contents will be accepted from either of the two inputs, up to a maximum capacity of 5000 items. The currently stored item and the quantity are displayed in the center of the building.

Any items over capacity or any dissimilar items will be blocked at the input, until either there is remaining capacity or the buffer has been emptied completely, respectively. The storage has the unique ability of priority outputs — though there are two belt outputs, the one on the left, marked with a green star & arrow, will be favored, using the right output only when there are additional items in the buffer.

In addition to the regular layer, storages also have two wire outputs, for detecting the buffer state. On the left side, it will output true when the storage is full and false otherwise. On the right, the currently stored item is output as a signal, or null if the storage is empty.

Uses

The primary usage of storage is to buffer enough items to smooth out peaks in demand, such as in MAMs. If items are only expected to be used in short bursts, then the supply factories only need to consistently supply the average requirements as opposed to the maximum at any given time, relying on the storage to accumulate extras during the slow periods.

While it's possible to create a hub dump system using the wire outputs, the comparatively low shape requirements for freeplay encourage more optimized item counter designs using a combination of splitters and readers.