How do I disable the display of popup which appears when holding down a key? It slows my typing speed and makes me do so many mistakes in my writing and programming. I need it at time when I wish to enter an alphabet twice.
In macOS, when a key is held down while entering text, a popup is shown which lets one choose between various accented forms of the character. To disable this execute the following command-line in the Terminal.app:
defaults write -g ApplePressAndHoldEnabled -bool false
Now, you'll need to log-out and log back in. This should disable the display of the popup and character typed should start repeating when the key is held down.
If you ever wish to return to this behaviour, execute the following command-line in the Terminal.app:
defaults write -g ApplePressAndHoldEnabled -bool true
You'll need to log-out and log back in again for the setting to take effect.