The Home button on your iPhone and iPad will get a new job with arrival of iOS 10: It’ll unlock your handset, replacing the old “Slide to Unlock” gesture. But you don’t have to wait until fall to change the Home key’s behavior.
Beyond its standard chores of taking you back to the home screen and letting you quickly switch between apps, the Home key can also act as a shortcut to some of iOS’s handiest features, such as zooming the display and reversing screen colors. You can also change the speed at which you need to double-click the Home key, or decide whether the Home button can access Siri and Apple Pay from the lock screen. Last but not least, you can choose whether double-touching the Home key engages iOS’s (potentially annoying) “Reachability” feature.
Read more here:: 5 ways to take charge of the iOS Home button