The Fujifilm Instax Square format was introduced in the summer of 2017. The dimensions of a picture are given as 8.6 by 7.2 cm. The captured image has a size of 6.2 by 6.2 cm and is surrounded by a frame. It is somewhat reminiscent of the Polaroid 600 or SX-70 format of the instant picture pioneer, but it is a bit smaller.
You can find an overview of the features of the different Instax Square cameras here.