I have been noticing a trend in apps I have asked to develop, also in apps developed by others and some of Google’s own apps, for example the default launcher on Nexus devices: A fix of app orientation to vertical.
There was a time when the advice was to develop apps so that they always dynamically handled any orientation. I think this came about because the original slide out keyboard-based Android G1 and popular Moto Droid relied on a horizontal screen. Rolling forward to more recent times, I am increasingly receiving designs that are vertical only with no thought or even hint that horizontal orientation has been considered.
Users are becoming more used to keeping smartphones vertical. Whether it’s because it takes effort to re-orientate a device or whether it’s a cause and effect of more apps becoming vertical-only, 29% of view time is now vertical vs 5% five years ago.
Vertical-only has the benefit of less to design and code and some types of content will never look great when horizontal. However, keep in mind there’s still a minority of phones, for example the Samsung Galaxy Stratosphere II where vertical-only apps are extremely difficult to use with the keyboard.
Should you make your app vertical only? I happen to be working on a specialised app, used for one purpose, on only one type of device, that fixes the app to landscape! Lists of things tend to work better on the vertical while image or vector based viewing, with panning, tends to work better on the horizontal. Take a deep look at your content and consider possible screen layouts before you decide. You might also like to take a look at how people hold their phones together with the context in which you expect your app to be used.