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I've gotten mixed answers from various websites and people concerning this question, and I wanted to put it out there for all of you to answer once and for all.

The question is, does force closing apps, (that is, double-clicking the home button, then swiping up on them), have any benefit to the battery or overall performance of an iPhone or any other iOS device?

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    @Tetsujin If you have an answer, please post it below, thanks. Comments do not have the features to edit or vet an "answer" as correct (or not). – Robert Cartaino May 9 '16 at 15:59
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There's been much debate and discussion around this topic. I believe it was beneficial for iOS back in the v3 and v4 days but now it's not.

Craig Federighi even came out recently saying it's not necessary and it doesn't increase the battery life. Apple has built-in their memory management the proper time to suspend and/or kill an app when necesssary. The only time you should force-close an app is if it has become unresponsive.

4

In one circumstance, a force quit can have a benefit to iOS that outweighs the cost of more processing needed to clean up the process, restart it, and purge any files that are cached/open.

The negative to doing this is that apps don't run in the background - so once you switch to a new app or the springboard / list of icons / lock screen - iOS has already stopped / paused / flushed all filesystem activity for the app.

It signals to a frozen app that it needs to fully reinitialize itself from scratch - disregarding any saved state or cached results. It signals to Apple in the form of a crash report (and optionally to the developer) some breadcrumbs exactly where the app was in the code when it was "killed" by the user.

  • In terms of performance - force quitting apps makes iOS and the app perform worse - measurably worse in many cases.
  • In terms of battery life - force quitting apps makes iOS and the battery life perform measurably worse as well.

Think of it like surgery - you are doing clear harm in the short term - unless you are sure surgery is needed, don't take the performance hit and force quit.

  • Don't think it's that simple. If the app uses a significant amount of resources while in the background (e.g. Facebook) and you don't intend to switch back to it for a longer time, the restart effort will be lower than the keep-it-running effort. – nohillside May 11 '16 at 10:20
  • @patrix I can't speak for Facebook in specific, but if an application is registered to run background services, iOS starts them right back up once you force quit - so unless the app is coded to not run when things auto-start - the force quit doesn't actually prevent a respawn of background threads/tasks - it just interrupts them, cleans up and then they run again. – bmike May 12 '16 at 0:20
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Lately this subject is a hot item again. I strongly believe it's useless to force quit apps on iOS devices. It's only helpful to restart apps when they crashed. Here more information.

9to5Mac:

It's been a long-standing belief in some circles that using the multitasking feature of iOS to force quit apps can help save an iPhone's battery life, or improve the speediness of the software when the smartphone becomes slow.

Earlier in the week, an iPhone user decided to email Apple CEO Tim Cook to put the issue to bed once and for all, and instead got a reply from Craig Federighi, Apple's senior VP of Software Engineering (via 9to5Mac).

Email Conversation

 

Here, from the official support document on forcing applications to close, is Apple’s own advice on when to use this feature:

When you double-click the Home button, your recently used apps appear. The apps aren’t open, but they’re in standby mode to help you navigate and multitask. You should force an app to close only when it’s unresponsive.

 

MacDailyNews quotes a 2010 email from Steve Jobs:

Just use [iOS multitasking] as designed, and you’ll be happy. No need to ever quit apps.

 

Just in case you don’t believe Apple’s senior vice president for software, Apple’s own official support documentation, or Steve Jobs, here are some other articles pointing out how this habit is actually detrimental to iPhone battery life:

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Theoretically, yes. Apps running at background do consume memory (their threads still exist and that's why you can see them listed when you double click the Home button), and thus they do consume battery.

But practically, not really. iOS does a fairly good job on memory management, and apps running at background only consume a small amount of memory. And if other apps running at foreground (actively running and users are interacting with them) need more memory, the iOS system may terminate the background apps and purge the memory. The reason that sometimes force-closing an app seems to save memory/battery life is because that, some apps may request to run long-running tasks even running at background, for the purpose of, for instance, background fetching, periodically syncing data, etc (note that not every app does that). But you can disable these by configuring Background App Refresh in Settings -> General.

So in summary, for an app that isn't doing much when at background, force closing it won't yield noticeable benefits.

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    "Apps running at background do consume memory (their threads still exist and that's why you can see them listed when you double click the Home button), and thus they do consume battery." This is not technically correct. What you see when you double-click the Home button is a snapshot (in memory) of the app when it was closed. Just because you see it there doesn't mean the threads still exist. iOS stops the app from running and removes it from memory unless it's been allowed to run in the background AND it's actively doing processing. – fsb May 9 '16 at 18:40
  • @fbara I don't agree. According to Apple's Developer doc, apps will go into a state called Suspended soon after going to background, and "while suspended, an app remains in memory but does not execute any code". The application's process is still there unless being terminated by iOS. If you have XCode(developer tool for iOS apps),you can actually use Debug->Attach to Process and see a list of processes on your phone, even if nothing is running at foreground – Stephenye May 9 '16 at 19:00
  • That same doc also states: "Shortly after an app delegate’s applicationDidEnterBackground: method returns, the system takes a snapshot of the app’s windows. Similarly, when an app is woken up to perform background tasks, the system may take a new snapshot to reflect any relevant changes. For example, when an app is woken to process downloaded items, the system takes a new snapshot so that can reflect any changes caused by the incorporation of the items. The system uses these snapshot images in the multitasking UI to show the state of your app." This is what I was referring to. – fsb May 9 '16 at 19:08
  • @fbara That's true: snapshots are used by the multitasking UI, especially for the purpose of not displaying sensitive data when entering background (used by some banking apps for example). But I think the process still exists. But let's not focus too much on the tech details here, regardless, it still consumes some memory (the snapshots still consume memory right). – Stephenye May 9 '16 at 19:27
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I have found that ending the Facebook app in particular can save battery life. After checking its usage in the battery section (Settings > Battery > Time), I can't help but be convinced that it's not playing nice.

  • This is because it registers itself as a VoIP client, and closing the app won't change that. – Andrew Larsson May 9 '16 at 19:49

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