The iPhone Duo is finally here. Apple's first folding smartphone arrives seven years after Samsung pioneered the category with the Galaxy Fold . That gave Apple plenty of time to refine the hardware behind closed doors rather than in public view—and the results show: The Duo is a pretty dang good foldable .

Whether your Duo just landed on your doorstep or you're still weighing that $1,999 price, here's what you need to know before unfolding it.

Apps Aren’t Optimized—Yet

Photograph: Julian Chokkattu

The iPhone Duo is a new shape and size for Apple, so many of your apps likely aren't optimized to show up properly on the unique 5.4-inch outer screen or the 7.6-inch inner display. Apple also changed how navigational elements appear on the Duo, aligning them on the right rail instead of centering them on the bottom like every other iPhone.

Apple apps, redesigned for the Duo, look great.…