Apple introduced a new animation in iOS 13 that appears on the screen when you press the physical volume buttons. Volume control slider appears on iPhone when you press a volume button.

An old friend returns to your iPhone lock screen with the iOS 18.2 update. You can bring back an on-screen volume control to the iPhone — provided you know which setting to adjust to bring back ...

labeled Always Show Volume Control. Enable the switch, and you'll be able to adjust volume from the Lock Screen without having to unlock your iPhone or use the physical volume buttons. Elsewhere ...