Title bar

A title bar does three jobs at once and is usually credited with only the first. It names the window, so a row of them in a task switcher can be told apart. It carries the window controls at one end. And it is the handle: the operating system treats the whole strip, minus the controls, as the region a drag moves the window by, which is why a bar with no empty space left in it is a window nobody can move.

Window controls are the buttons, the title bar is the strip that carries them, and the difference matters as soon as an application draws its own. A toolbar is the other neighbour, and the two are distinguished by who owns the commands: a toolbar holds actions that act on the document, while the title bar belongs to the window manager and acts on the window. A unified bar is what a platform gets when it merges those two strips into one, putting the document’s tools and the window’s name on a single line. It buys back a whole strip of vertical space, and it costs the drag region that space used to provide, so a unified bar has to keep some of itself empty on purpose.

The bar is also where a window says whether it is the one you are talking to. An inactive window dims its title, its controls, and often the bar’s own fill, while the content below stays legible. That dimming is a real signal rather than decoration: on a desktop covered in overlapping windows it is frequently the only thing distinguishing the window that will receive the next keystroke from the four behind it. Dim the bar, never the document.

Because it is the first thing drawn and the last thing customised, the title bar is where platform style shows itself most plainly: the striped, glossy lozenges of Aqua, the translucent Mica backdrop tinted by the desktop behind it, the chiselled grey caption bars that retro web design reaches for when it wants a page to look like a 1998 application. Web apps that draw a title bar of their own inherit the whole contract with it, including the part where a reader expects to be able to grab it.