Here’s how to do it: open any app that brings up the keyboard, press down and hold the key with the emoji symbol, then choose from the three modes that are illustrated with keyboard symbols. If you want to switch back to the standard keyboard, tap on the back arrow that appears in the empty space next to the keys. You can also set one of the one-handed modes as the default keyboard across your phone by going to the Settings app, then choosing General > Keyboard > One-Handed Keyboard and selecting which one you want to appear every time you want to type something in an app. That's it.
Sure, one-handed keyboard modes are a small change (and one that other phones and third-party keyboards have offered for a while), but if you've ever struggled to text on your iPhone 6S Plus while holding onto a subway poll with your other hand, then your life is about to get a little easier. You can download and install the iOS 11 update in the Settings app when Apple releases it on Tuesday.