With the release of the Samsung Galaxy S8, S8+ and the LG G6, a new 18:9 (in the case of Samsung, 18.5:9) is making its way to Android devices and Android developers will need to support it. If developers don’t update the maximum aspect ratio of their apps, their apps will be rendered at 16:9 on these devices. That means that users will have a black bar at the top and bottom of the display. It’ll work, but won’t be so pretty.
In a blog post on the Android Developer blog, Google has posted on this and is encouraging developers to increase the maximum ratio of their apps to support this new 18:9 view so their apps can take full advantage of the screen size.