A toolbar appears at the bottom of an app screen and contains buttons for performing actions relevant to the current view or content within it. Toolbars are translucent, may have a background tint, and often hide when people are unlikely to need them. For example, in Safari, the toolbar hides when you begin scrolling the page since you are likely reading. You can show it again by tapping the bottom of the screen. Toolbars are also hidden when a keyboard is onscreen.
Provide relevant toolbar buttons. A toolbar should contain frequently used commands that make sense in the current context.
Consider whether icons or text-titled buttons are right for your app. Icons work well when you need more than three toolbar buttons. When you have three buttons or fewer, text can sometimes be clearer. In Calendar, for example, text is used because icons would be confusing. The use of text also allows the Inbox button to show a count of calendar and event invitations.
Avoid using a segmented control in a toolbar. Segmented controls let people switch contexts, whereas a toolbar is specific to the current screen. If you need to provide a way to switch contexts, consider using a tab bar instead. See Tab Bars.
Tip It’s important to understand the difference between a toolbar and a tab bar, because both types of bars appear at the bottom of an app screen. A toolbar contains buttons for performing actions related to the current context, such as creating an item, deleting an item, adding an annotation, or taking a photo. A tab bar lets the user switch quickly between different sections of an app, for example, the Alarm, Stopwatch, and Timer tabs in the Clock app. See Tab Bars. Toolbars and tab bars never appear together in the same view.