A message dialog is an overlay UI element that provides a stable and contextual surface that is always modal and explicitly dismissed. Message dialogs appear at a consistent location on the screen.
Use message dialogs to ask for explicit action from the user or to deliver a message that is important for the user to acknowledge. Examples of usages of dialogs are the following:
- The user is about to permanently alter a valuable asset
- The user is about to delete a valuable asset
- The security of the user's system could be compromised
Use custom dialogs when the app or the system must invest a significant amount of time in the ensuing actions such that an accidental dismiss would be detrimental to the user's confidence.
All dialogs should clearly identify the user's objective in the first line of the dialog's text (with or without a title).