When you’re done with an app on the Mac, you quit it. Many people do the same on the iPhone, where you can double-press the Home button to access the App Switcher and then swipe up on an app to quit it. But just because you can do it on your iPhone (or iPad), doesn’t mean you should. Worse, contrary to what some people believe, quitting iPhone apps will likely hurt battery life.
iOS on the iPhone (and the iPad) thinks differently about how apps run compared to the Mac. When you’re using an app, let’s say Safari, it’s accessing the iPhone’s CPU and radios and thus using battery power. However, a few seconds after you press the Home button to return to the Home screen or lock the screen by pressing the Sleep/Wake button, the iPhone puts the app into a state of suspended animation. It’s almost like it puts the app to sleep. In that state, it’s not using CPU or battery power, but it does remain resident in memory, which turns out to be important.
Imagine that you next open Notes, which becomes the active app and starts consuming CPU, memory, and battery resources. Tap a Web link in a note, and your iPhone suspends Notes and takes you back to Safari. Because Safari was suspended earlier and thus is still in memory, it’s faster and easier for your iPhone to activate it than to launch it from scratch. If Safari was not in memory, it would use more resources, including more battery, to open back up. It would also be slower, as it has to load into the iPhone’s memory.
Now as you continue switching among apps, there may not be enough memory for each app to remain suspended, so your iPhone will quit apps to free up enough memory. There’s no way to know when your iPhone has done this; it’s invisible to you. If you try to help your iPhone by quitting apps manually, you’ll force it to waste more resources later when those apps have to be launched again.
Are you curious on how many apps your iPhone has suspended? Swipe far to the right in the App Switcher (double-tap on the Home button); it probably lists many more apps than you’d expect. Again, this is not a list of running apps; it’s a list of previously used apps. These apps are suspended, or as I like to say, sleeping. They are still in your iPhone’s memory, but they are not running or using resources. When you need to open them again, they will use less resources when opening than if they were quit out of.
So, 98% of the time, there’s nothing to gain and some speed and battery life to lose by quitting apps. But there are two legitimate reasons to quit apps: to restart a frozen or confused app, and to prevent certain background apps from using power unnecessarily.
Although it’s unusual for iOS apps to freeze or misbehave, it can happen, so if an app isn’t responding, or if it’s acting weirdly, quit it. That usually solves the problem; if it doesn’t, you might need to download an update or delete the app and reinstall it from the App Store.
iOS on the iPhone allows some apps to run in the background instead of being suspended. For instance, if you use Maps, you want it to keep tracking your location and providing turn-by-turn navigation even if you’re using Podcasts. Similarly, iOS allows some apps, like Skype, to listen for incoming calls in the background. There are a few other categories of allowed background apps—audio apps like Podcasts, for instance—but in all cases, if you’re trying to preserve as much battery life as possible, consider quitting background apps whose services you don’t need. For example, if you park before arriving at your destination, you might quit Maps to ensure that it doesn’t continue to track your location. And if missing an incoming call is less important than saving some battery power, quit Skype.
But these are infrequent exceptions to the rule. Most of the time, quitting apps is a waste of both your time and your iPhone’s battery. I hope the tip helps!