Menu bar

A menu bar is the row of words at the top of a desktop application: File, Edit, View, Help. It is always there, it holds no commands itself, and every command the program has is meant to be reachable through it. That completeness is the contract. A toolbar shows the handful of actions worth a button; the menu bar is where the rest live, in an order people have known since the 1980s.

Its defining behaviour is what happens after the first press. Opening one menu arms the whole bar: from then on, passing the pointer over another title switches to that menu without a second click, and moving off the bar does not close anything. The bar has entered a mode, and it leaves that mode only when a command is chosen, Escape is pressed, or something outside is clicked. This is why a menu bar is worth naming separately from a row of independent menu buttons, which each need their own press.

The keyboard contract matches. The whole bar is a single tab stop, not one per title. Left and Right Arrow move along the titles, Down Arrow opens the menu under the current one, Up and Down move inside it, Escape steps back out, and typing a letter jumps to a command starting with it. This is exactly the case role="menubar" and role="menuitem" were written for, and one of the few places on the web where those roles are honest: a site header full of links is navigation and should not borrow them.

Platforms differ about where the bar lives. macOS keeps one global bar at the top of the screen belonging to the frontmost application; Windows and Linux put it inside each window, and modern Windows apps often fold it into a single overflow button. On the web the pattern is rare outside editors and IDEs, where the density of commands justifies it, and it competes with the command palette, which answers the same completeness problem by search instead of by hierarchy. Both can coexist: the bar teaches the vocabulary, the palette is faster once you know it.