Give another Mac’s app your whole ultrawide

Your MacBook’s screen may be small. The app running on it does not have to be.

Beam puts a window from one Mac onto another: the window itself, on your desktop, at its own size, with its own Dock icon and a place in ⌘ Tab. We call this a beamed window. It sits beside the local windows on the Mac in front of you.

With Beam, the other Mac’s bezel stops being the ruler for its windows.

Your canvas should set the window’s size

An ultrawide gives you one continuous area for a large working canvas, references and communication. macOS can resize windows manually and arrange them in halves, quarters and multi-window layouts.

Those layouts divide one Mac’s desktop. They do not bring an individual app from a second Mac into that desktop. That distinction matters in a multi Mac desk setup.

Three ways to put two Macs on one ultrawide

There are three useful arrangements:

1. Picture-by-Picture shows two computer inputs at once. LG describes it as displaying two connected inputs simultaneously. Each Mac receives a section of the panel.
2. An input switch changes which Mac occupies the monitor. A monitor with a KVM can also switch the connected keyboard and mouse. Dell documents both Picture-by-Picture and a built-in KVM.
3. Beam brings the useful app from the other Mac onto the undivided desktop in front of you. It becomes a window, not a screen, so you can arrange it among local apps.

The common hardware-led setup connects both computers, shares the peripherals, then adds window-management software. Beam changes the unit being moved. Instead of dividing or switching the monitor, you beam the particular window you need.

Build a designer’s wide workspace

Start with both Macs running Beam on macOS Sonoma or later. On the same network, Beam discovers other Macs running Beam locally, without asking anything outside the network. Pair them once and the connection is encrypted and pinned to those two machines.

Then build the workspace:

1. Open the design app on the other Mac.
2. Choose its window from the picker. The picker is where you select the window or display to beam.
3. Place the beamed window on the ultrawide attached to the Mac in front of you.
4. Drag its edges until the working canvas occupies the dominant region.
5. Keep local references, messages or a browser in the remaining regions.

The beamed window has its own Dock icon and place in ⌘ Tab. A Mac window on another monitor therefore behaves as an independently arranged part of your current workspace, rather than as a rectangle inside a shared screen.

Resize the real window beyond its display

Drag a corner of a beamed window and the real window resizes over there. Type into it and the keystrokes land in the app, shortcuts included. Toggle the speaker and that app’s audio plays on this Mac.

The real source window can grow beyond the physical display attached to the other Mac. The app receives the larger window dimensions, and Beam streams the resulting picture at the size you are viewing. The picture is streamed at your display’s exact resolution, so text stays crisp.

This is why a smaller source display does not impose its dimensions on your ultrawide. Beam is resizing the app window itself, not stretching a fixed picture captured at the other screen’s size.

Why the other Mac’s screen stays put

While you work in a beamed window, nothing moves on the other Mac’s screen. Only the window you picked is shared; hidden windows and password managers never reach the picker.

Beam shares one window at a time, or a whole display when you pick one. Your visible workspace on the other Mac can remain arranged for someone sitting there while you work with the selected app on the ultrawide.

A Mac without an attached monitor works too. A headless Mac gets a virtual display from Beam at Retina density. A virtual display is a drawing surface that macOS treats like a screen even though no physical panel is attached. The same idea extends naturally to running a headless Mac mini from your desk.

Ultrawide or dual displays is a task decision

Screen layout should follow the work. A 17-participant study of ultrawide and dual-display configurations found that results depended on the task. Its 34-inch curved ultrawide, used at a longer viewing distance, produced neck motion similar to a single 24-inch display and could reduce screen interactions. Dual displays retained advantages for work that benefited from flexible screen positioning.

For a designer who wants one large canvas with supporting windows nearby, an ultrawide offers a coherent surface. Beam lets an app from the other Mac claim the region that work requires.

Check the display and connection

You can use an ultrawide monitor with a Mac when the Mac, monitor, connection and cable support the resolution and refresh rate you want. Apple notes that external-display capabilities vary by Mac model. You can set resolution and refresh rate in Displays settings, and Apple notes that scaled resolutions can affect performance.

Both Macs run Beam. They talk directly over the local network, or over your Tailscale tailnet when apart. No account, no server, no cloud. A tailnet is the private network Tailscale creates between your devices, allowing paired Macs in different places to reach each other directly.

The result is one wide desktop, arranged around the work rather than the hardware that happens to run each app.