Alert dialog box

An alert dialog box is a special dialog box that is displayed in a graphical user interface when something unexpected occurred that requires immediate user action.

The typical alert dialog provides information in a separate box to the user, after which the user can only respond in one way: by closing it. Closing an alert dialog will provide access to the original window, which is not available while the alert dialog is presented.

Alert dialogs that block the application are regarded as a bad design solution by usability practitioners, since they are prone to produce mode errors. Also when used as error dialogs, they have been shown to be ineffective in their goals to inform users about an error condition or protect from a destructive operation.

Alerts have several typical uses:

Warning and question alerts typically offer two opposite options to close the dialog ("Allow/Deny", "OK/Cancel", "Yes/No") with the implicit assumption that one will proceed with the paused process that triggered the dialog, and the other one will interrupt the process without action. A good practice in interface design, often included in Human Interface Guidelines, is to label each option with the precise effect that it will have on the process (for example, "Save/Don't save" in a dialog triggered while editing a document with unsaved changes).

The primary reason for using an alert dialogue instead of communicating via the main program window is Modality. A typical online form is non-modal. They present to a user many actions that can be performed in any sequence. By contrast an alert dialogue creates a modal state that isolates a particular element of the form and requires a user to address it before proceeding to the next step.

The utility of the alert dialogue is increasing with mobile device penetration, because:

alert() is the name of the method used in JavaScript to spawn an alert dialog. The argument to the method is the text to be displayed in the window.

A dialog created this way will contain a yellow triangle warning symbol (similar to those found on electrical devices), the text of the warning message, and a single button saying "OK" which will close the window.

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