In an analysis of website performance in Mobile Safari on the iPad, the study's authors note that "the content is readable, but the links and widgets are too small to touch reliably." According to research, the target size for a tappable area should be no smaller than one square centimeter; anything smaller than that size makes it difficult to interact with a link or object, and it can even lead to tapping another object completely by mistake. This can be mitigated somewhat via zooming gestures, but overall the study recommends giving users plenty of room to interact with objects on your site.
Other recommendations for website usability on the iPad run from removing or providing alternatives to Flash content (a given since the iPad doesn't support Flash and probably never will) to making bigger touch targets and padding them to prevent the frustrating onset of "fat finger disease" that iOS users know so well. The authors also recommend that sites minimize the need for users to type in order to interact with your site, because study participants found the iPad's on-screen keyboard cumbersome and frustrating to use compared to a "real" keyboard.
Nielsen Norman recommends that services avoid making an iPad app just so they can say they have one, because the study found that apps tended to be more poorly-designed than sites for the same service. iPad apps tended to contain less content than sites, and some apps had a confusing design or a UI that worked against user expectations rather than with them. "Do not make users work more in your iPad app than on your website," the authors advise, citing numerous examples of apps that went for a glitzy design that didn't satisfy user expectations.
"If you decide to have an iPad app, make sure that the app delivers extra value, compared to the website," the authors state. Your app should provide some kind of hook to it that your website doesn't have rather than presenting a stripped-down interface, because "whenever apps lack features, users quit them for the websites." The authors also emphasize that iPad apps should not be designed the same way as iPhone apps.
Apart from the fact that the iPad's screen is much larger and offers more opportunities for interactivity, the study also found that the usage paradigm is different between the iPad and iPhone. Users tended to be seeking quick access to small blurbs of information while using an iPhone, like looking up addresses or brief product reviews while comparison shopping; by contrast, study participants said they tend to use the iPad in a more leisurely fashion under circumstances that don't require such rapid access to content, and they're also looking for a more in-depth experience on the iPad.
One of the cardinal sins of app design that the study authors note is apps requiring user registration before allowing access to content. The study found apps that force users to register before accessing content will drive users back to registration-free sites; study participants seemed very intolerant of anything they considered an impediment to accessing content, and being forced to register via the iPad's on-screen keyboard before being able to interact with an app was an instant turn-off.
Splash screens were another impediment to content access that the study authors found in many apps. "Several new iPad apps have long introductory segments that might be entertaining the first time, but soon wear out their welcome," the authors note. "Bad on sites, bad in apps. Don't." This is a recommendation that I'll back wholeheartedly. I have an app on my iPad that I use every day, the New Zealand Herald, and every time I launch it I have to sit through a short introductory film that serves absolutely no purpose except to show off (and make me wait before accessing anything). It's worse than the show-off introductory Flash animation that's been the plague of far too many websites since the mid-2000s, because there isn't even a "skip intro" link for me to frantically search for and tap.
Once users have access to the app's content, creating an easily navigable UI is crucial to their experience. "Ideally, the app should be functional without instruction," the study notes. "If you must use instructions, they should be memorable and simple." Though the study doesn't mention it specifically, I've found Flipboard to be a good example of a self-explanatory UI. When the app launches, the "Flip" tag on the right side of the screen tells you about two-thirds of what you need to know about interacting with the app. The study found that apps with more obtuse UIs, like the Moleskine app, had such lengthy and confusing instructions that most users simply abandoned the app altogether.
As for the UI elements themselves, Nielsen Norman recommended making them as obvious as possible, noting that "users don't know that something is touchable unless it looks so." They noted that Sears' app was a good example of an iPad app that did not follow this design sensibility, which had the effect of needlessly complicating navigation, rendering sections of the app undiscoverable through casual use, and confusing users. The authors recommended "making buttons look tappable and relevant to the task they accomplish. This means choosing the right icons and labels for those buttons or action links."
The full study is available for free and is a fascinating primer on the dos and don'ts of designing apps for the iPad. I couldn't find a single point that I disagreed with, and when thinking about the iPad apps that I use and enjoy the most, I found that nearly all of them have UIs that function well within what the Nielsen Norman Group recommends. If you're interested in designing apps for the iPad, or even simply questioning whether your site or service needs an iPad app at all, I'd highly recommend giving their study a close read.
[via Ars Technica]