Does the iOS today extension install automatically on user's device along with the host app?

I just need a little information about iOS's today widget, if a user installs an app with this extension, is it compulsory for him to later manually add the widget from the dedicated menu, or can this widget be installed automatically at the same time as the app?

Thanks.

Today extension aka Widget automatically get installed with hosted app. User have to just go to Widget screen, then there is Edit button at bottom. Click on edit screen - will show all the widgets available on given device.

See the Edit button in below screenshot. It is showing that 8 new widget available on given device. If you click on that button and can press + button to show in widget screen and can press - screen to hide it.