The single biggest misconception about iOS is that it’s good digital hygiene to force quit apps that you aren’t using. The idea is that apps in the background are locking up unnecessary RAM and consuming unnecessary CPU cycles, thus hurting performance and wasting battery life.
That’s not how iOS works. The iOS system is designed so that none of the above justifications for force quitting are true. Apps in the background are effectively “frozen”, severely limiting what they can do in the background and freeing up the RAM they were using. iOS is really, really good at this. It is so good at this that unfreezing a frozen app takes up way less CPU (and energy) than relaunching an app that had been force quit. Not only does force quitting your apps not help, it actually hurts. Your battery life will be worse and it will take much longer to switch apps if you force quit apps in the background.
Here’s a short and sweet answer from Craig Federighi, in response to an email from a customer asking if he force quits apps and whether doing so preserves battery life: “No and no.”
Just in case you don’t believe Apple’s senior vice president for software, here are some other articles pointing out how this habit is actually detrimental to iPhone battery life:
I see people regularly force quitting their apps all the time – people who do this are idiots.