Drag-and-drop is one of many user interface techniques designed to move objects on a computer. The "drag" action involves keeping the main mouse button—left-click by default—depressed, and then gesturing the mouse towards a destination. The "drop," on the other hand, involves releasing the main mouse button over the target destination. This technique allows for multiple applications in computer use, including file relocation and arrangement. Some programs use the drag-and-drop method to simplify certain commands, such as data input.
The technique replicates a natural human motion for moving objects. By treating the mouse pointer as a "hand," users can grab, move, and put different virtual objects down. This intuitive design is an industry standard among operating systems, usually helping make computer use more accessible to the average person.
Software programmers add drag-and-drop functionality to their applications for ease of use. Several email clients, for example, allow file attachments to be dragged and dropped into an outbound message. This saves the user the time and effort usually reserved for locating and attaching the file through a separate dialog box. The drag-and-drop technique is also used for different games, office programs, and other software in which virtual objects are moved. With the development of HyperText Markup Language version 5 (HTML5), websites can include drag-and-drop functionality within the code, allowing for more user-friendly interfaces.
Many touch-screen devices use the method as the basis for their user-interface techniques. Rather than tapping the screen multiple times to navigate through the device, users can simply keep their fingers on the screen and "drag" towards the desired destination. The "drop" stops movement. Given the small screen sizes on handheld devices, the drag-and-drop might need to be performed multiple times before the desired result is achieved. This allows for quicker use of the device, as well as reduces wear and tear on the screen.
There are certain limitations to the drag-and-drop method, however. In transferring files, both the original location and target destination must be open during the procedure. Although this is often a negligible problem, it is still possible for the destination to be layered underneath the original location, making the desired new location inaccessible. The remedy for this issue is the drag-and-drop itself; the destination simply has to be dragged and dropped to an area of the screen away from the file's original location. Other problems arise when designers alter the convention, as in the case of computer trackpads; in lieu of buttons, users often need to tap the pad twice before using the drag-and-drop.
