Zoom is an Accessibility feature that makes everything from text to icons to interface elements bigger and easier to see on the iPhone and iPad. Zoom magnification defaults to 200% but can be set from 100%-500% to help anyone with low vision of any level. When in zoomed mode, all the standard navigation and selection gestures — tap, swipe, and pinch — work just like normal. Zoom can even work alongside VoiceOver to provide even greater assistance for those with visual impairments.
Note: Designers use zoom as well to help check pixel-level details on-screen.