Learn How iOS Multitasking Really Works

Fraser Spiers debunks the common ‘tip’ he frequently hears about how people should kill iOS multitasking apps as they ‘slow down’ your iPhone.

To counter this incorrect advice he details specifics about how multitasking works on iOS, and how the system is smart enough to manage itself on its own. It’s a comprehensive read for all iOS users:

You may think that, if an app is resident in memory, you have to somehow remove it to conserve memory. You don’t because iOS does it for you. If there are Suspended apps lying around and you launch a memory-intensive app such as a big game, iOS will start to purge Suspended apps and move them to the Not Running state. That is, they will be completely removed from memory and will launch afresh the next time you tap their icon.

Where some people get confused is this: all of the above has no impact on what you see in the multitasking bar. The multitasking bar always shows a list of recently used apps, regardless of whether they’re in the Background, Suspended or Not Running states. You may also have noticed that the app that is currently Active does not appear in the multitasking bar.

Here is Apple’s own description of multitasking, a featured that debuted last summer with iOS 4.0:

Multitasking in iOS allows you to switch instantly between apps and to resume an app. When you return to an app, you can pick up right where you left off. Multitasking doesn’t slow down the performance of the foreground app or drain battery life unnecessarily.

As much as I agree with the intuitiveness of iOS to manage itself, I found killing apps in the multitasking tray did speed up my former iPhone 3GS and iPhone 4 (not so much on the iPhone 4S–it’s blazing).

Don’t we all remember the Cydia tweak ‘Remove Background’? One test you can do yourself is run an intensive app such as iMovie with the multitasking tray full versus emptied, and tell me if you notice a difference. It’s a debate I’ve had numerous times with friends.

Do you force close multitasking apps? Or do you put your trust into iOS?

[via BrooksReview]

Founder and Editor-in-Chief of iPhoneinCanada.ca. Follow me on Twitter, and @iPhoneinCanada, and on Google+.

  • Alex Sebenski

    The reason you may notice that your iPhone works faster after closing apps is the following:
    The apps in the background are using RAM to hold in suspended state. As you use applications the actions you take may require more RAM than currently allocated to that application so it’s our phone must close one of the apps in the background. This closing of background apps before performing the action you requested by clicking a button or scrolling around the app is the slow down you’re seeing.
    By closing the applications in the background you are freeing up this RAM in advance making your actions happen faster, but it required you do more work manually yourself.
    Make your own decision which you prefer.

  • Anonymous

    If I leave apps open overnight vs closing them before I sleep makes a big difference on the battery drain.

    To me it’s not about speed or memory management. It’s the battery drain

  • Anonymous

    I think Alex hit it spot on which is why I wish Apple would at least give users the option to remove all background processes ourselves instead of having to do it manually.

    Apple hates giving people choices. 🙁

  • Daniel Lee

    Agreed 100%, I close my apps when I am done with them, I don’t leave them hanging because I can have my iPhone sit idle and powered on for a few days with no apps running in the background, but if I leave a few running the battery is dead when  I wake up in the morning.

  • esper

    As a developer, I can assure you that all most apps consume while in a background state in RAM, which is freed automatically when requested by the operating system.

    However: certain applications may use location services in the background which has the potential to drain your battery rather fast. To know if this is your case, check the OS status bar (on top). If you see a little compass arrow lit, then one of your apps is currently actively using location services.

    To find the culprit, jump to the Location Services section of Settings. Apps with a grey arrow are apps that have used location services in the last 24 hours. Apps with a purple arrow are actively using location services. These apps will drain your battery if you leave them running.

    Otherwise, battery drain should not occur at all since the operating system does not allocate *any* resources to background apps (no app, other than location services and background music app may use processor cycles while in the background).

    Obviously, if your device is jailbroken, these rules might not apply!

  • Anonymous

    I usually don’t close them with one exception: the GPS apps. Those must be closed as soon as u’re done with them for 2 reasons: they eat most of the RAM and they use location services in the BG so not only they slow the phone down, but they drain the battery pretty much.

  • Weebsurfer

    I do it all the time. I’m sorry, but this fella has drank way to much of the Apple flavored kool aid. There’s ram being used by background apps and there is bound to be fragmentation of memory. I hope apple gives the option to clean up processes or even just reduce the number left there. But I doubt they’d ever do it as gracefully as the JB apps do.

  • Sevael

    I also agree.  Certain apps in the background have a very noticeable affect on my 4S’s battery life.  Noticeable enough that in a mere half hour I can see the difference between having an app in the background or killed entirely.  It’s easily confirmed using the official Twitter app:

    Start with a fully charged phone and a fresh reboot.  Kill all background apps.  Set Twitter to NOT use location services.  Now open Twitter, wait for it to load the latest tweets, then press the home button to return to the springboard and then lock the phone.  Leave it overnight.  Upon checking the phone in the morning, my battery has drained an average of 25% in standby (when NO calls, texts or emails are received).

    Repeat again the next night under all the same circumstances but make sure the Twitter app is killed in the multitasking tray first.  After the same amount of time in standby, surprise surprise, my battery has only drained 7 – 9%.

    Just for the record, my iPhone 4 sans Twitter only drained 2 – 4% overnight with all the same settings, but that’s another issue entirely.

  • Anonymous

    Whatever Apple, clearly it doesn’t work as intended or at all. I had to use SBS settings to clear out all these apps running in the background because it didn’t take long to run out of ram on my 3GS. I’d start with about 100MB of RAM free and after opening a few big apps it’d run out of memory and have about 6MB free. The phone would run like shit so I’d have to clear them myself. I’m sure this is a non-issue on more powerful phones as they have ample memory to support tonnes of apps.

  • Chris

    I’m in the same boat minus SBS settings. Open up a few apps on my 3GS and it kills the ram, causing everything to run super slow. Killing all apps helps with said problem.

  • ThatGuy

    I find when launching the app initially it is sluggish, I guess because of iOS working in the background to send my apps in the “not running” state. Other than the launch I would say performance is the same.

    I did my tests on infinity blade, mc3, asphalt 6, iMovie and logmein.

  • Mtfail

    Apple employees also need to be educated about this because a nimrod there told me that you have to kill the apps because they are running in the bg since they show up in the multitasking bar. I told him no that’s just a list of recently used apps and it doesn’t necessarily mean that they are all open and killing them will have no effect. He told me I was wrong. I didn’t bother to argue with him but there is clearly a misunderstanding of this in the Apple org.

    Apple really messed up abt the memory management with multitasking though. If I need to kill apps in order for me to use my phone, then MT has failed. Whatever happened to “it just works”?

  • Mtfail

    Apple employees also need to be educated about this because a nimrod there told me that you have to kill the apps because they are running in the bg since they show up in the multitasking bar. I told him no that’s just a list of recently used apps and it doesn’t necessarily mean that they are all open and killing them will have no effect. He told me I was wrong. I didn’t bother to argue with him but there is clearly a misunderstanding of this in the Apple org.

    Apple really messed up abt the memory management with multitasking though. If I need to kill apps in order for me to use my phone, then MT has failed. Whatever happened to “it just works”?

  • Woody

    I always remove backgrounded apps. I use backgrounder to kill all apps from the multitsking tray except for the ones I want to run. If I dont remove apps the iphone 4 slows down. I dont care what Apple says. It slows the phone down and drains the battery. If I leave one app in the multitasking tray my battery will drain like 10% over night. If I remove all the apps, my battery stays at 100%

  • Anonymous

    There has to be a better way to kill apps. Over time i got zillions open and killing them manually one by one as the only option is just silly. I stopped killing them but my iphone just killed itself and wouldnt start. It had to be reset. It choked on having too much apps opened.

  • Rogers-c

    I would kill the apps just to make sure im not using data unnecessarily!

  • Jozsef Varga

    I force close them every few weeks, mostly because an Apple Store Employee told me too.