Two monitors, one menu bar: where your icons live on an external display
· 6 min read
Connect an external display to a Mac and the menu bar starts behaving oddly. Sometimes it appears on both screens, sometimes only one. Icons move. Clicking a window on the second display changes where the menus are.
The behaviour is consistent; it is governed by two settings and one rule that is not obvious.
The rule
Each display gets its own menu bar, and the menu bar on a given display shows the menus of whichever application is active. The active display is the one containing the window you last clicked.
So the menu bar follows your attention, not your cursor and not a fixed screen. Click a window on the external display and the menus appear there. Click back to the laptop screen and they move back.
That single rule accounts for most of the apparent inconsistency.
The setting that changes everything
System Settings, Desktop & Dock, then Displays have separate Spaces.
On (the default) means each display is independent. Each has its own menu bar and its own full-screen behaviour. A full-screen app occupies one display and the other keeps working normally.
Off means the displays are treated as one continuous desktop. There is a single menu bar, on the primary display only, and a full-screen app takes over everything.
Changing this requires logging out and back in, which is why people change it once, forget, and later find the behaviour inexplicable.
If your menu bar appears on only one display and you expected it on both, this setting is switched off.
Choosing the primary display
The primary display is where the menu bar lives when separate Spaces is off, and where new windows tend to open.
System Settings, Displays, then Arrange. Drag the small white bar at the top of one screen’s rectangle onto the other. That moves the primary designation.
The same panel is where you set the physical arrangement, and getting that right matters more than it seems: if the arrangement does not match how the displays actually sit on your desk, moving the pointer between them feels wrong in a way that is hard to identify.
Where status icons appear
Status icons appear on whichever display currently has the menu bar. They are not duplicated; they follow.
That means an icon which does not fit on the laptop’s bar may fit comfortably on an external display, because there is more width and no notch. This is a genuine reason a missing icon reappears when you connect a monitor. When a menu bar icon disappears covers the underlying space problem, and what the notch does covers why the laptop bar is tighter.
The order of the icons is per user, not per display, so an arrangement you set with Command-drag carries across.
Closed-lid operation
Running a laptop closed with an external display connected, sometimes called clamshell, changes one thing worth knowing: there is only one display, so all the above collapses to the simple case.
For a time record, the useful detail is that a Mac in clamshell mode with power connected does not sleep when the lid closes. It keeps running, and it keeps recording. A Mac on battery with the lid closed and no external display does sleep, and nothing is recorded. Sleep, screensaver and lid close covers what each state does to a day.
Displays and a day’s record
Two things that surprise people.
Disconnecting a display does not interrupt tracking. Windows rearrange, sometimes untidily, and the frontmost application is unchanged, so the record continues.
Connecting a display can briefly change which application is frontmost, as windows move and something takes focus. It shows up as a few seconds attributed to whatever grabbed focus, which is not worth worrying about.
Where Punchcard sits
Punchcard puts one item in the menu bar, so it appears on whichever display currently has the bar, and moves with it.
It records the frontmost application by name regardless of which display that application’s window is on, so a multi-display setup makes no difference to the record. At the closing time you set, it prints a receipt of the day wherever the menu bar currently is.
Because the icon is a way in rather than the mechanism, a display change or a crowded bar costs visibility rather than data. The best way to track time in the menu bar covers what a status item should be responsible for.
Questions
Can I have the menu bar on both displays at once? Yes, with separate Spaces on. Each shows the active application’s menus, and the icons appear on whichever display has focus rather than on both.
Why do my windows move when I disconnect? Windows on a disconnected display have to go somewhere and are moved to the remaining one, often untidily. macOS remembers arrangements per display configuration and usually restores them on reconnection.
The external display’s menu bar is a different height. Scaling. Different resolutions and scaling factors produce different bar heights, which is normal.
Does a second display affect battery? Yes, noticeably. Driving another display costs power, and the compositing work rises. It is one of the larger single factors in laptop battery life.