Minecraft wiki entry for Barrel, associated text: To open the barrel GUI, use the Use Item control. To move items between the barrel inventory and the player inventory or hotbar while the barrel GUI is open, drag or shift-click the items. Holding Alt and double-clicking while holding an item moves all items of the type clicked on in or out of the barrel to the extent that space is available for them.‌[Java Edition only] To exit the barrel GUI, use the Esc control.