Remember that the keyboard should never get in the way of what the user is trying to do, and you’ve got most of the UX solved right there. Your job is to meet or exceed those expectations. Try to maintain those features as well in addition to your features or services. the default iOS keyboard is responsive, clean, responds dynamically depending on the type of text entry, provides autocorrection and text replacement, and just works. The success of your keyboard, depends on ability you provide features, expectations of users.

your custom keyboards must be with user trust, means what they type, it should pass the same to host’s view.This gives you the freedom to use any of the iOS supported unicode characters. They convert these actions into Strings and send them to the host text input view. Your custom keyboard extensions need to provide UI that handles user interactions, such as button taps.If you long press on it, it shows the all existing ones, then you can choose as well. By tapping it, next keyboard(the next one from available keyboards from device) will replace by the existing one.

We can see on default keyboard, a globe button at the bottom.

Every keyboard in IOS must provide a button to change the keyboard.

Once user added this keyboard to his list on his device, it can be used by not only your application, but all other applications on user’s device except some which restricted the extensions from their bundles(APP Delegate).

Custom keyboard extension let the users add additional keyboards to the list of available keyboards(system keyboards).

Apple has come up with a great future like App Extensions, Which are giving an option to replace system functionalities by your own creations.

Ios custom keyboard swift