Hagaki paper is a postcard-sized paper that is 4 inches by 4 inches and is slightly thicker and heavier than standard printer or photo paper. It is also used to refer to a print size when producing pictures. It can also be referred to as the Japanese postcard size, but printers equipped with this option are sized to 3.94 inches by 5.83 inches.
Printers produced and used outside of Japan do not have a setting for hagaki paper size, although many commercial printers do have the Japanese postcard option. If the printer being used does not have the proper setting, it can be set to a 4 inches by 6 inches setting to accept the paper, which is standard on most printers.