BlurBox
Help · How-to

Use BlurBox across multiple monitors

Overlays move freely between displays, and glued overlays follow their windows wherever they go.

Last updated: April 2026
A multi-monitor setup with BlurBox overlays on both displays
Overlays work the same on every display.

Free-floating overlays

Drag any unlocked BlurBox between monitors just like you would any other window. Once you let go on a different display, the overlay sits there until you move it again. BlurBox doesn't treat monitors specially — overlays exist in your global screen coordinate space and work everywhere.

Glued overlays

When you move a window between displays, any BlurBox glued to that window follows along automatically. The overlay leaves the first display, briefly stretches across the gap (if your displays aren't edge-to-edge), and settles on the new display matching the window's new position.

During a fast cross-screen dragSome apps animate the window translation across displays. The overlay tries to follow in lockstep, but you may see a small visual lag during very fast drags. The overlay snaps to the correct final position when you release the window.

Display-specific scenarios

Sidecar (iPad as a second display)

Works like any other extended display. You can drag overlays onto the Sidecar screen and glue them to apps running there.

AirPlay mirroring

BlurBox overlays show up on the mirrored display because they're regular on-screen windows. This is the desired behavior for most privacy use cases — if you're mirroring your screen to a TV or projector, the audience sees your blurs.

Different display scales

Overlay sizes are stored in points, so a BlurBox keeps its physical size when it moves between displays of different pixel densities (e.g., a Retina internal display and a 1× external monitor). The blur quality is rendered natively on each display.

Limitations

  • Display arrangement changes. If you replug a monitor or rearrange displays in System Settings, glued overlays may temporarily detach until you click their target window once.
  • Closed-lid clamshell mode. Closing your MacBook lid while an external display is connected works fine, but BlurBoxes that were on the laptop screen will move to the external display.

What's next?