iOS Multitasking: Stop Force Quitting Applications

iOS Recently Used Applications about to be Force Quit

iOS Recently Used Apps about to be Force Quit

I see this happen more times than I care to admit. Friends, acquaintances, and even strangers in public toying with their iPhone, pulling up the recently used apps list and killing everything. Not just a single app, but every last item, including the “Phone” and “Messages” application. If this is you, stop it. Stop it right now.

The flawed logic here is that with less things running, they will achieve better battery life or have the iOS device perform better on the task they are currently working on. And it makes sense; anyone that has ever used a laptop knows that the battery will die quicker if you’re multitasking heavily instead of running a single lightweight application.

iOS takes a more battery-conscious approach to multitasking because it is specifically designed to be used in a mobile environment. Even though I’ve read about this claim in the past, until now I never had a solid source to back up the talk. Recently, iOS developer Fraser Speirs posted an excellent video (below) explaining iOS Multitasking that answers many of these mysteries. I take absolutely no credit for the video, but it’s something that anyone who practices obsessive task-quitting should watch.

iOS Multitasking Explained

In this demo, he uses an iPad, but the same principles apply to an iPhone or iPod Touch, as they are all iOS devices.

Before publishing this video, Fraser wrote an detailed technical blog post about how iOS manages applications. I encourage you to visit his site and read up more on this topic for those that want a more exhaustive explanation.

Too Long; Didn’t Watch

Fraser demonstrates that once home button is pressed, the currently running iOS app immediately stops using the CPU and will be suspended in memory. If you launch another application and it needs more memory than is currently available, iOS will automatically force quit, or kill suspended applications as needed to make room for the currently running app.

Some incorrectly call the menu that comes up when double-tapping the home button the “Task Switcher” or “Multitasking Screen.” This gives the false impression that these iOS apps are still active and running. The screen should be better know as the “Recently Used Apps List.” It will list applications even if they have been completely ejected from memory.

Fraser explains that there are only five types of applications that are allowed to run in the background:

  • Apps that play audio while in the Background state. A good example is Instacast while it’s playing a podcast.
  • Apps that track your location in the Background. For example, you still want voice prompts from your TomTom navigation app, even if another app is Active.
  • Apps that listen for incoming VOIP calls. If you use Skype on iOS, you can receive incoming Skype calls while the app is in the Background.
  • Newsstand apps that are downloading new content.
  • Apps that receive continuous updates from an external accessory in the Background.

Applications of this nature will continue to use the CPU in the background until their suspension conditions are met. As soon as those tasks are complete (e.g. your destination is reached/the download is complete) all well-behaved apps will immediately be suspended, and stop consuming any CPU time.

So unless you have a critically low battery that you absolutely need to save for another task AND are currently using a program that falls into the five categories listed above, stop micro-managing applications on your iOS device.

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21 Comments

  1. Michael
    Posted May 8, 2012 at 6:47 am | Permalink

    Nope.

    Some internet apps will be slower with others opened in the background, some apps and games will be super slow.

    If you’re experiencing a problem, closing apps will probably fix it. It’s not about this unique situation you make up in your conclusion sentence.

    • Erick
      Posted May 8, 2012 at 5:08 pm | Permalink

      100% agreement with your statement.

      There are Games that will tell you that there’s not enough memory to run and to close apps, after closing open apps the game now runs flawlessly.

  2. Matt
    Posted May 8, 2012 at 7:03 am | Permalink

    Some apps are poorly written, and are a HUGE drain on battery (OnTime, I’m looking at you!). They need to be killed when you are done using them so you can have more than a 4 hour (idle) battery life.

  3. Gautam
    Posted May 8, 2012 at 8:44 am | Permalink

    iOS also has a app launch timer I believe. So if an app doesn’t launch in some X seconds, its killed and freeing up memory takes time. So in low memory conditions, sometimes your new app launches and sometimes it doesn’t. What is guaranteed is that it takes longer for apps to launch in low memory conditions. That might be reason enough to kill apps!

  4. Alex Matijaca
    Posted May 8, 2012 at 12:56 pm | Permalink

    There are apps that are badly behaving… They get into a funky mode, and no matter how many times, you try to start-up the app, the said app starts in this funky state (because that ‘bad’ state is persisted somewhere). If you really kill the app, by double clicking home button, and killing the app from there, next time you start it, it’s just fine…. There are times when this is a very valid thing to do…

    • Posted May 8, 2012 at 1:12 pm | Permalink

      I completely agree with you. There are times that apps become unresponsive, get caught in loops, or just act “funky.” If you kill the misbehaving app as you mentioned, it will typically solve the problem. However, using the recently used apps list to force-kill a series of well-behaved programs is not going to accomplish anything that the kernel will do for you automatically.

      • bill
        Posted May 9, 2012 at 12:08 am | Permalink

        Just like killing the apps is not accomplishing anything negative. Maybe you should spend less time judging people in public and worry about your own iPhone.

        • Posted May 9, 2012 at 12:37 am | Permalink

          I am in no way judging a persons character by the way they handle their iPhone. It’s a common misconception that everything in the recently used apps list is eating memory and I wrote this post to explain why that is not true.

          If you feel better by having a “slim” recently used tasks list, then that’s your prerogative. I know many people that think that everything listed is active in RAM and I simply wanted to explain that it not the case.

          It’s a recently used apps list that has the ability to force quit applications, not a “task manager” that lists everything currently loaded in memory. Although subtle, there is a big distinction between the two.

  5. Posted May 9, 2012 at 9:47 am | Permalink

    Nice post. iOS has an excellent multitasking management and the user has little control over it.

    The practical use I have for the “Recently Used Apps” bar is to do what it was intended for in the first place: quickly re-open apps I used recently.

    The ONE AND ONLY OTHER USE for it is to kill buggy aps that insist on not working correctly. Sometimes, the app will not work as intended and the quickest way to recover is to wipe it from memory, forcing the whole app to reload from scratch again.

  6. Nick
    Posted July 7, 2012 at 2:51 am | Permalink

    Then why is it that when I force quit all my apps in my “recently used” apps my ram jumps from about 200mb to over 300? I can see this because I’m jailbroken and shows my ram in my notification center.

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