Feedback helps people know what an app is doing, discover what they can do next, and understand the results of actions.
Unobtrusively integrate status and other types of feedback into your interface. Ideally, users can get important information without taking action or being interrupted. Mail, for example, subtly displays status information in the toolbar while navigating through mailboxes of messages. This information doesn’t compete with the primary content onscreen, but can be checked at any time with a quick glance.
Avoid unnecessary alerts. An alert is a powerful feedback mechanism, but should be used only to deliver important—and ideally actionable—information. If people see too many alerts that don’t contain essential information, they quickly learn to ignore future alerts. For additional guidance, see Alerts.