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Mac keeps swapping your monitors or the main display? How to make it stick

By Aqib Javed · Updated Oct 10, 2026

macOS saves a display arrangement for each set of monitors, but it can mix them up after a plug-in or wake, especially with two identical monitors, docks or DisplayLink adapters, because the displays come back in a different order or with new IDs. Set the arrangement in System Settings, Displays, Arrange. To keep it from changing, use a tool that reapplies it: displayplacer if you're happy with the command line, or DisplayShift, which puts your arrangement back by itself.

Set the arrangement you want

  1. Open System Settings, then Displays, and click Arrange.
  2. Drag the screens so they match where they sit on your desk. Moving the pointer between them should feel natural.
  3. To choose the main display, the one with the Dock and where new windows open, drag the white menu bar onto it.
  4. Click Done.

Why it changes on its own

  • Two monitors of the same model can look identical to macOS, so after a wake it may swap which is which.
  • Docks, hubs and DisplayLink adapters can bring displays back in a different order.
  • Plugging a monitor into a different port can make it look like a new display.

Keep it from changing

displayplacer is a free command line tool that prints your current arrangement as a command you can run again later, for example from a script or a shortcut. It's precise, but you have to run it each time things go wrong.

DisplayShift does it without commands. Leave Keep my screen arrangement on (Settings, Screens). It learns the arrangement you set yourself for each set of screens, and when a plug-in or wake swaps your monitors or changes the main display, it puts your arrangement back before any windows move. Mirrored displays are left alone.

Questions

How do I change which monitor is the main display on a Mac?

Open System Settings, Displays, Arrange, and drag the white menu bar onto the monitor you want as the main display.

Why does my Mac swap my two identical monitors?

Identical monitors can report the same details, so macOS can't always tell them apart after a wake or reconnect. A tool like DisplayShift or displayplacer can put the arrangement back.

Will DisplayShift fight me when I change the arrangement myself?

No. It only learns from changes you make while the same screens stay connected, and only restores after a plug-in or wake.