When I first upgraded from my iPhone 4 to the iPhone 5s, I immediately noticed an incredible upgrade in the clarity and sharpness of the larger 4-inch Retina display, but also some usability issues that plagued my iPhone usage experience for the following months. That’s why I’m excited for the pixel tripling 3x mode at 1704 x 960 resolution Apple is currently testing for the iPhone 6, but simultaneously worried about the day to day use of iOS on a larger 4.7 or 5.5-inch device. Apple explained it best:

Apple currently recommends developers focus specifically on the upper left portion of the iPhone display for important navigation functions and considers the lower right portion of the screen “less important” (pictured above from Apple’s developer documentation). That’s not going to fly with a larger 4.7-inch+ display, and it’s got me wondering if app developers will have to fundamentally rethink the layout of apps in addition to any changes to support the next iPhone’s increased resolution.

The question is whether or not Apple’s standard navigation buttons and recommendations for app developers will need to change to accommodate a different experience with the larger display. After all, iOS as we know it and Apple’s guidelines for apps seem to be specifically suited to a 4-inch or smaller display. It’s also something third-party devs should be thinking about outside of Apple’s recommendations. Take Apple’s standard back button for instance (pictured below). It resides in the upper left corner of the display, just out of thumb’s reach for many people when upgrading to a larger 4.7-inch+ display.

From Apple’s developer guidelines:

Make it easy to focus on the main task by elevating important content or functionality. Some good ways to do this are to place principal items in the upper half of the screen and—in left-to-right cultures—near the left side of the screen

Currently in iOS 7, Apple reserves the bottom of the iPhone’s screen for tab bars and toolbars. They look like this:

However, for the Navigation Bar, Search fields and scope or filter buttons, Apple recommends devs use the top of the iPhone display and that’s where you’ll find them and many other main navigation buttons along the top of most of your favorite apps (pictured right). Additionally, Apple’s Notification Center feature is activated using a pull-down gesture from the upper edge of the display. Of course, these issues aren’t present in iOS on the larger screen of an iPad because tablets are meant to be used as two-handed devices. With a smartphone meant for one-handed use, reaching everything with your thumb on a larger display can make for quite a clunky user experience. Ask Android users.

Gestures could be one way developers decide to workaround no man’s land on the iPhone 6. Apple has a one finger gesture that it recommends using “to return to the previous screen,” but that doesn’t replace the back button in Apple’s apps or the majority of third-party apps. Safari uses it for going back and forth between webpages, lots of Apple’s stock apps still use the standard back button in the upper left, and other apps use it for everything from pulling out a sidebar, to cycling between tab views and swiping through photos. Ideally a new gesture could become a standard for the back button in apps, but that doesn’t address the rest of the navigation buttons commonly found along the top of the iPhone display.

But everyone wants a bigger screen iPhone, right? Android has 5, 6, 7, and even 8-inch smartphones and it seems to be doing pretty well, right? Unfortunately Android shipment numbers and the stats on people wanting bigger displays don’t mean iOS won’t encounter some usability issues with a larger display. You don’t hear many people shouting about how much better the user experience is on those crisp, large screen Android smartphones.

Let’s take a look at Android: Notification drawer at the top of the screen ✓, search bar at the top of the display ✓, many navigation buttons at top of screen ✓, tons of complaints in reviews over devices being uncomfortable to hold ✓, usability issues with reaching buttons at the top of the screen during one-handed operation ✓. It’s pretty easy to see that Android has all the same issues as iOS that were noticeable on a 4-inch display but about to get a lot worse on an iPhone with a bigger display. Android does, however, put the all important back button in the bottom left corner of the screen that allows users to move back through previous screens across the OS as well as dismiss onscreen dialogs, popups, etc. It’s one of the most used buttons and makes navigating Android on a larger display much less frustrating than I imagine it would be on iOS.

One thing both the LG Optimus G2 and soon G3 and Samsung Galaxy Note do is have a mode that puts the UI elements in the bottom right or left corner when being used in “single hand mode”. Below is a video of the Galaxy Note:

Even if Apple and developers address these usability issues that get introduced with the larger display, perhaps a market for a 4-inch or smaller high-end smartphone will emerge in the process. I’m not just worried about the navigation problems, I’m also not too excited about lugging the larger device around in my pocket. To quote Steve Jobs, “ I’ve reviewed and lived with the high-end smartphones from HTC and Samsung that currently dominate the market and, UI issues aside, the hardware feels unwieldy compared to my iPhone. If these issues do exist on iPhone 6, I’d definitely consider switching to a high-end, 4-inch or smaller Android device should one be released.

Of course Apple could do that too. If Apple does eventually go with the 3x resolution it’s currently testing for iOS 8 and the iPhone 6, it wouldn’t just make it easy for developers to update image assets for the new device, but also make it easy for developers to continue supporting users with 4-inch devices with the current Retina resolution. It could easily continue to offer a 4-inch device alongside the new 4.7 and 5.5-inch next-gen iPhones to cater to that market, but that doesn’t change things for usability issues for devs that want to support the larger screen sizes.

Is it possible I just happen to have tiny, boyish hands and didn’t know it? Nope. According to the most studies I dug up online, my hands are almost exactly the national average for men: 7.5 inches in length.

I’m admittedly now somewhat used to my 4-inch iPhone, but my hands certainly aren’t getting any bigger. I already think buttons along the top of the screen are uncomfortable on the 4-inch iPhone and, considering I don’t have particularly small hands, I can imagine this could be an issue for a large number of iOS users.

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