In
user interfaceThe user interface is the aggregate of means by which people—the users—interact with the system—a particular machine, device, computer program or other complex tool...
design, a
modal window is a child window that requires the user to interact with it before they can return to operating the parent application, thus preventing the
workflowA workflow consists of a sequence of connected steps. It is a depiction of a sequence of operations, declared as work of a person, a group of persons, an organization of staff, or one or more simple or complex mechanisms. Workflow may be seen as any abstraction of real work, segregated in...
on the application main window. Modal windows are often called heavy windows or
modal dialogs because the window is often used to display a
dialog boxIn graphical user interfaces, a dialog box is a special window, used in user interfaces to display information to the user, or to get a response if needed. They are so-called because they form a dialog between the computer and the user—either informing the user of something, or requesting...
.
Modal windows are commonly used in GUI systems to command user awareness and to display emergency states.
In
user interfaceThe user interface is the aggregate of means by which people—the users—interact with the system—a particular machine, device, computer program or other complex tool...
design, a
modal window is a child window that requires the user to interact with it before they can return to operating the parent application, thus preventing the
workflowA workflow consists of a sequence of connected steps. It is a depiction of a sequence of operations, declared as work of a person, a group of persons, an organization of staff, or one or more simple or complex mechanisms. Workflow may be seen as any abstraction of real work, segregated in...
on the application main window. Modal windows are often called heavy windows or
modal dialogs because the window is often used to display a
dialog boxIn graphical user interfaces, a dialog box is a special window, used in user interfaces to display information to the user, or to get a response if needed. They are so-called because they form a dialog between the computer and the user—either informing the user of something, or requesting...
.
Modal windows are commonly used in GUI systems to command user awareness and to display emergency states. In the web, they are often used to show images in detail.
Relevance and usage
Modal windows are more common in the
Microsoft WindowsMicrosoft Windows is a series of software operating systems and graphical user interfaces produced by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces...
world, where modal windows frequently are an element of
Multiple Document InterfaceGraphical computer applications with a multiple document interface are those whose windows reside under a single parent window , as opposed to all windows being separate from each other . In the usability community, there has been much debate over which interface type is preferable...
applications, than in that of
Mac OSMac OS is the trademarked name for a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
,
UnixUnix is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
-derivates, and the
X Window SystemThe X Window System is a computer software system and network protocol that provides a graphical user interface for networked computers, and was initially developed as part of Project Athena...
. In these OSes, many features that would be represented by modal windows in Windows are instead implemented as
transientA transient screen is a pop-up screen such as a notification or dialog screen on a mobile phone.It covers only part of the screen as well as dimming the remaining area...
windows. Transient windows behave similarly to modal windows they are always on top of the parent window and are not shown in the window list, but they do not disable the use of other windows in the application.
Use Cases
Frequent uses of modal windows include:
- drawing attention to vital pieces of information. This use has been criticised as ineffective.
- blocking the application flow until information required to continue is entered, as for example a password
A password is a secret word or string of characters that is used for authentication, to prove identity or gain access to a resource . The password must be kept secret from those not allowed access....
in a loginIn computer security, a login or logon is the process by which individual access to a computer system is controlled by identification of the user using credentials provided by the user.A user can log in to a system to obtain access and can then log out or log off In computer security, a login or ...
process.
- collecting application configuration options in a centralized dialog. In such cases, typically the changes are applied upon closing the dialog, and access to the application is disabled while the edits are being made.
- warning that the effects of the current action are not reversible. This is a frequent interaction pattern
Interaction design patterns are a way to capture optimal solutions to common usability or accessibility problems in a specific context. They document interaction models that make it easier for users to understand an interface and accomplish their tasks....
for modal dialogs, but it is also criticised by usability experts as being ineffective for its intended use (protection against errors in destructive actions) and for which better alternatives exist.
Criticisms
A modal window blocks all other
workflowA workflow consists of a sequence of connected steps. It is a depiction of a sequence of operations, declared as work of a person, a group of persons, an organization of staff, or one or more simple or complex mechanisms. Workflow may be seen as any abstraction of real work, segregated in...
in the program until the modal window is closed.
Users may not recognize that a modal window requires their attention, leading to confusion about the main window being non-responsive, or causing loss of the user's data input (see Mode error). However, many interface designers have recently taken steps to make modal windows more obvious and user friendly by darkening the background behind the window or allowing any mouse click outside of the modal window to force the window to close, a design called a
LightboxLightbox, and the newer Lightbox 2, is a JavaScript application used to display large images using modal dialogs. The script has gained widespread popularity due to its simple yet elegant style and easy implementation...
, thus alleviating those problems - even if not completely.
Sentiments against modal windows inspired some of the primary guidelines in early human-computer interface work. Microsoft's use of
wizardsA wizard is a user interface element where the user is presented with a sequence of dialog boxes. Through these dialog boxes, the user is led through a series of steps, performing tasks in a specific sequence...
for example, was seen as excessive in Windows 95.
Still, modal windows are an integral part of common GUI toolkits and are frequently used when designing user workflow. Believing that too many active
modeless dialogs can lead users into confusion, proponents of modal windows advocate reducing the amount of user input at a given time. This, they argue, can reduce user confusion, while minimizing the likelihood of an error as a result of having too many modeless windows open concurrently.
Usability practitioners oppose these claims arguing that restriction of user actions for the sake of usability is an error, since this leads to user frustration for no benefit. User input is necessarily entered at one place at a time, as it requires conscious attention anyway. Users can handle complex amounts of information, given that it's presented in a well-structured and logical design, by performing a preliminary general scanning and then centering their attention in the tool required to complete a goal; complex goals will often require switching attention from one point to another.
Unexpected
alert dialogsAn alert dialog is a colloquial term for a particular type of dialog box that occurs in a graphical user interface...
are particular culprits of mode errors with potentially severe consequences. Usability practitioners prescribe that dangerous actions should be undoable wherever possible; an alert box that appears unexpectedly or which is dismissed by
habituationHabituation is the psychological process in humans and animals in which there is a decrease in psychological response and behavioral response to a stimulus after repeated exposure to that stimulus over a duration of time.- Background :...
will not protect from the dangerous action.
Thus, the proposed correct solution to the problem would be to design every input element as a small, self-contained,
task-orientedTask analysis is the analysis of how a task is accomplished, including a detailed description of both manual and mental activities,task and element durations, task frequency, task allocation, task complexity, environmental conditions, necessary clothing and equipment, and any other unique factors...
interaction (i.e. guided by the data dependencies required to complete a goal, not the interface states hardwired by the coder).
For example, changing a visual aspect of the input element to reflect an invalid entry (such as applying a red border), or adding a character such as an
asteriskAn asterisk is a typographical symbol or glyph. It is so called because it resembles a conventional image of a star. Computer scientists and mathematicians often pronounce it as star...
next to any input element that needs to be filled in. This way, presenting several simultaneous input elements would be a benefit to the user, since they could switch easily from one to another following their flow of consciousness instead of being coerced into a predefined programmed path.