You have probably grown so accustomed to your iPhone's SpringBoard animations when opening and closing apps that you hardly notice the animation where apps spring onto your screen when you open them and then fade away when you close them. You can reduce this animation by going to Settings > General > Accessibility and turning on the Reduce Motion setting. But this setting only reduces the motion and falls short of getting rid of it entirely.
For a completely animation-free iOS experience, you'll need to exploit a glitch that a Reddit user found. With it, apps launch instantly and close instantly. Here's how to go about it:
1. Head to Settings > General > Accessibility. In the Interaction section, open AssistiveTouch and turn it on.
2. Move the little AssistiveTouch menu icon to the lower-right corner of your screen.
3. Swipe down on your screen to call up Spotlight search, which moves the AssistiveTouch menu icon from the bottom edge of the display to the top of the onscreen keyboard.
4. Swipe down or tap the screen to close Spotlight search, which then moves the AssistiveTouch icon back to the bottom edge of the screen. Do this enough times, moving the AssistiveTouch icon up and down, and you will trick iOS into disabling its SpringBoard animations.
You will know the glitch has worked when the AssistiveTouch icon drops back to the bottom of the screen without a pause when you close Spotlight search. Before this change takes effect, the AssistiveTouch icon pauses briefly before it moves.
On Reddit, the poster says to repeat steps 3 and 4 of opening and closing Spotlight search 20 times. In my experience, it sometimes took up to 30 times to get the change to take effect, and other times it took only four or five attempts. I was able to make it work on an iPhone 6S and iPad Air, with both devices running iOS 9.2. Also, it didn't work on my iPad Air until I turned off Multitasking gestures, which is noted in the Reddit post. Head to Settings > General > Multitasking and toggle the switch off for Gestures.
After you have disabled animations, you can go back to settings and turn off AssistiveTouch to get rid of its menu icon and still enjoy an animation-free iOS experience. This trick, however, works only until the next time you restart your iPhone; if you turn off your iPhone, the animations will appear the next time you power it back on.
In related news, you can speed up your Android by adjusting animation settings.