Android
One-handed Mode for Keyboard auf Android
One-handed mode shrinks the Gboard keyboard and pins it to the left or right edge of the screen, closing the gap between your thumb and the farthest keys.
The setting lives inside the keyboard's own preferences, not the general Accessibility menu, which is why many users search for it without success.
To turn it on or off, go to Tap on Settings ➔ Tap on System ➔ Tap on Keyboard ➔ Tap on On-screen keyboard ➔ Tap on Gboard ➔ Tap on Preferences ➔ Tap on One-handed mode ➔ Select Off, Right-handed mode or Left-handed mode.
Right-handed mode shifts the keyboard to the right edge, left-handed mode moves it to the left, and Off restores the full-width layout.
Once active, a small arrow icon appears next to the keyboard to expand it back to full size temporarily or switch sides again.
One-handed mode only affects Gboard's layout, so a case, screen protector or a different keyboard app will not change how it behaves.
If typing still feels cramped after switching sides, check whether a third-party keyboard app is set as default instead of Gboard, since the toggle only works inside Gboard's own preferences.