Modal dialogs serve as gatekeepers for essential actions in the user journey. They appear when users' authorization or permission is required to proceed with the current task.

These dialogs maintain context while obtaining necessary approvals. For instance, when unregistered users attempt to save content, a modal requests authentication without disrupting their browsing experience. Similarly, location-based services use modals to request permissions that enable core functionality.

Non-modal dialogs offer a less disruptive alternative for collecting optional information that doesn't block the main task flow. These work well for feedback surveys or preference settings where immediate action isn't required.

Complex data entry requiring multiple fields should avoid dialog interfaces entirely. On mobile devices, navigating through form fields in a confined space creates unnecessary friction. Such interactions benefit from dedicated screens that provide adequate space and a clear structure for data input.