frontmost

Frontmost is an adjective that denotes being at the front or the most visible part of something. It is used to describe objects that are closest to the observer or to the front surface in a stack, layer, or scene. For example, in photography a frontmost subject is the one in the foreground. In maps or diagrams, the frontmost feature is the one drawn on top of others. The term is formed from front and -most and has been in use in English since at least the early modern period.

In computing and graphical user interfaces, frontmost typically refers to the window or application that currently sits at the front of the screen and has input focus. The frontmost window is the one that receives keyboard input and is visually on top of other windows. The frontmost application is the active program the user is interacting with. In macOS and some scripting contexts, the frontmost application is a precise technical term; Windows discussions often distinguish foreground windows or processes, which in practice overlap with the idea of frontmost but can have specific OS-level definitions. Users should be aware that frontmost and foreground are related but not always interchangeable across platforms.

See also: foreground, topmost, active window, z-order.