Twitter recently released a complete redesign for all major platforms, in part the redesign has been made to unify the experience across platforms.
But, because of this goal I couldn't help noticing the iOS version has the menu/navigation bar at the bottom of the screen:
The web app's menu is at the top bar:
As is Android's
This difference is easily the most visible difference between the apps and can make the experience slightly confusing when switching between the iOS and other versions. The previous Twitter iOS app had the menu bar at the bottom too.
Why is the menu bar at the bottom on iOS? This visibly harms their cross-platform unification, so there must be some reason beyond "it's the way the old app was" as the apps were all changed despite that.
Because the Apple iOS Human Interface Guidelines say it should be there:
Appearance and Behavior - A tab bar appears at the bottom edge of the screen and should be accessible from every location in the application. A tab bar displays icons and text in tabs, all of which are equal in width and display a black background by default. When users select a tab, such as Search in YouTube, the tab displays a lighter background (which is known as the selection indicator image) and its icon receives a blue glow.
This place makes more sense too, because when you are touching the tabs, your hand/fingers are not blocking the rest of the screen, as there are when using the Android version.
In my opinion the menu bar should be in the bottom in mobile apps, because there you can easily reach the buttons, when using your phone with one hand!
"This visibly harms their cross-platform unification"
Why is that important? I propose that it isn't, and can actually be a detriment.
For instance, I work on a team building web apps. We are given marching orders to support iPhones and new Androids, as well as BlackBerries running old OSes and Nokia phones.
That, in and of itself is fine, but we have management and even UX that looks at these devices side-by-side and get upset when they don't match to the pixel across each device...which is just absurd for a variety of reasons:
As for why to put the menu on a touch device at the bottom, it's because that's usually where your thumb is at. ;)