A page control shows the position of the current page in a flat list of pages. It appears as a series of small indicator dots, representing the available pages in the order they were opened. A solid dot denotes the current page. Visually, these dots are always equidistant, and are clipped if too many appear onscreen. Users can tap the leading or trailing edge of a page control to visit the next or previous page, but they can't tap a specific dot to go to a specific page. Navigation always occurs sequentially, usually by swiping the page to one side.
Don’t use a page control with hierarchical pages. A page control doesn’t show how pages are related or indicate which page corresponds to each dot. This type of control is designed for pages that are peers to one another.
Don’t display too many pages. More than about 10 dots are hard to count at a glance, and more than about 20 open pages are time-consuming to visit in sequence. If your app needs to display more than 20 pages as peers, consider using a different arrangement—such as a grid—that enables nonsequential navigation.
Center page controls at the bottom of the screen. A page control should always be centered and positioned between the bottom of the content and the bottom of the screen. This keeps it visible, without blocking content.
For developer guidance, see UIPageControl.