iOS 9 App Switching and the Back-to-App Button

When people use their phones to plan dinner out with friends on a Friday night, there is often a lot of back and forth between different apps — looking up restaurant ratings on an app such as Yelp, checking restaurant availability on OpenTable, and synchronizing with everybody in their party through email and SMS. Research recently published confirms that users who look for information on their mobile phones often interact with more applications and for longer — on average, they interact with 4.6 different apps and launch apps 10.8 times within the same information-seeking session (compared with only 2.6 apps and 3.9 launches per session in other types of sessions, such as browsing sessions).

So there is definitely a need to support mobile multitasking and combining multiple sources of information, or, at least, switching back and forth between multiple apps.  Besides going back to the home screen and launching a second recently used app by tapping on its icon, there are two quick ways to switch between apps:

1. Go to the list of recent apps, find the app you’re looking for, and tap on it. (In iOS this is done by tapping the Home button twice; in Android by tapping the Recent Apps physical button.)
2. Use the Back button.

Until iOS 9, the second option was only available to Android users: the phone’s physical Back button works across applications and thus allows users to go back to a previous app, provided that the current app was launched from the previous one. In other words, if someone sent you a link in an email and you tapped on it while reading the message in the Gmail app, the link would be launched in the browser and once you’ve finished reading the page you’d be able to go back to Gmail by tapping the phone’s Back button. However, if you decided to stay on that site and browse one more page, tapping the Back button would not take you back to the app, but to the page you’d seen before in the browser’s history. In other words, the Android physical Back button has a meaning that is fairly easy to understand by the users: it undoes the previous action.

With iOS 9, Apple introduced some changes to how users can switch between apps: not only did it redesign the list of recent apps, but it also introduced a new Back-to-app button.  The new list of recent apps displays the different apps in a stack of cards, not unlike the stack of cards used for the same purpose in Android. But Android makes better use of the limited screen space, by stacking cards vertically instead of horizontally and by using a fish-eye effect to still fit in some of the apps used farther away in the past.

However, one of the most notable changes in iOS 9 is not the new list of apps, but rather the new Back-to-app button. Unlike the Android physical Back button, the iOS Back-to-app has a very limited functionality: In certain circumstances, it allows people to go back to the previous app they used.

Issues with the Back-To-App Button

As usability experts, we are trained to look for and see the worst in interfaces. So let me preface my list of complaints by admitting right away that the Back­-to-App button is definitely useful since it decreases the interaction cost of switching apps. However, the implementation creates some potential issues. Luckily app designers can alleviate at least one of these problems.

1. Target size. First, it is obvious that the Back-to-app button is an afterthought — it feels almost like a Band-Aid on a beautifully finished product. Its size is tiny and its position at the very top of the screen makes it easy to accidentally hit other buttons that apps traditionally place in the top left corner of their design (for instance, the hamburger menu or the in-app Back button).

   Although is hardly noticeable because of the small size, its lack of discoverability is likely not a huge problem: since this is an operating system (and not a random app or website), users will have many opportunities to eventually notice it and hopefully learn to use it.

   

2. Mental model. The Back-to-app button only takes users back to a previous app if the current app has been invoked by that previous app. In other words, if you’re listening to a song in Pandora, then double tap the phone’s Home button to invoke the list of recent apps, and finally select iTunes from that list to look for the same song, there won’t be a Back to Pandora button displayed in iTunes. However, if you tap a shopping-cart icon in Pandora and it takes you to iTunes directly, then the Back to Pandora button will be displayed.

    

   Some users will have a hard time understanding precisely why the button sometimes appears up at the top of the screen and sometimes doesn’t. Because of this apparently nondeterministic behavior, people may end up not relying much on the button and opting instead to use the other, more beaten and reliable path, of switching apps  — namely, hitting the phone’s Home button twice to invoke the list of recent apps. The designer’s mental model of the Back-to-app button is not easily conveyed to the user.

   Something that always works is preferable to something that sometimes works. (Because if it always works, it’s a no-brainer to reach for it. But if it only works sometimes, there’s a risk in looking for the feature, only to be disappointed. People don’t like disappointments and, once disappointed, they may not reach again for the same feature.)

   Moreover, the Back-to-app button is not recursive — you can only go back one level. So if you click on a link in Mail and it takes you to the App Store to download, say, IMDb, and then you open IMDb, you will only be able to navigate back to the App Store, but not back to the Mail app using the Back-to-app.

   The only one level of Back may not seem like a big problem. After all, users’ working memory is limited and they are unlikely to keep track of a long chain of apps that they’ve used over time. However, remember that users do use the Back button repeatedly on web browsers to retrace their steps until they return to a safe place, such as their browsers’ homepage.

3. Conflict with the in-app Back button.If you land on a deep page within an app, often the top left corner of that screen is taken by the Back button. But what does the Back button mean when this is the first page you’re seeing in that app? In the Yelp example above, what would Back take you to  — the previous page you’ve visited in Yelp the last time you’ve used the app? Who can remember what that page was, especially if your last session wasn’t so recent?

    

   Although that button in Yelp does take users to the previously visited page (in this case Nearby), laudably, Yelp has likely realized very quickly the potential for confusion, since an update seems to have fixed this problem by labeling the button Nearby instead of Back.

   

   

   From the three issues pointed out here, this is the only one that can actually be fixed by app designers. And the fix is an old design recommendation: do not call a button Back unless it undoes the previous action taken by the user. Like it or not, this is the behavior of Back that users have come to expect from their experience with the browser Back button on the desktop. If there is a circumstance in which the Back button does not undo the last action taken by users, then increase the information scent by labeling that button with the name of the page that it leads to.

A Note on Apps Invoking Apps

With iOS 9, Apple has made it easier for an app to directly give control to a different app. A potential danger that lurks on this road is user disorientation. When apps can seamlessly invoke other apps it is easy for users to get confused and think they are in the wrong app. For instance, clicking on a link in Pandora sends users (seamlessly) to iTunes, but since iTunes does not display any logo on the page or in the navigation bar, it’s easy for people to miss that they are in a different app (admittedly slightly less easy now, because the Back-to-Pandora button offers a supplementary cue, should the users be inclined to notice it and make the right inference).

Until recently, we used to say that apps don’t need a logo because users usually know what they’ve launched. If you expect your app to be invoked by other apps, seriously consider adding a logo in the navigation bar even on deep pages to tell people where they are. Otherwise, they may be not notice that they were switched to a new app and be confused when they don’t see the content that they expect.

Conclusion

Being able to directly invoke an app from another app is not a completely new feature in iOS, but the Back-to-app button offers more support to it and allows users to switch easily between two apps. We’ll see if applications will take advantage of this feature and call other apps, or rather, in the spirit of keeping users more and more within their own cage, will prefer to continue serving mobile pages within browsers. In any case, if you’re planning to embrace this feature, make sure that (1) you add information scent to a within-app Back button by labeling it with the name of the page it points to; and (2), you show the app logo on deep pages within your app.

Reference

J.P. Carrascal, K. Church. 2015. An In-Situ Study of Mobile App & Mobile Search Interactions. CHI '15. http://doi.acm.org/10.1145/2702123.2702486