Use another computer as a second monitor

Last updated Invalid Date

A second monitor is usually a purchase. If there’s another computer on your desk — a laptop that got replaced, a desktop you keep for one program, a machine you test on — its screen can be that monitor instead.

What Extend actually does

When you press Extend, EasySwitch asks your operating system to create an additional display. It is a real one as far as the system is concerned: it appears in Displays settings, you can arrange it left or right of your existing screens, and windows move onto it the normal way.

That new display has nothing on it. EasySwitch encodes it and sends it to the other computer, which shows it full-screen. Only that display is streamed — your existing desktop is not captured, recorded or mirrored, and with Extend switched off nothing of the kind leaves the machine.

This is the difference between EasySwitch and screen mirroring. A mirror copies a screen you already have, so it can’t give you more room to work. Extend gives you more room and shows it somewhere else.

Start and stop

1. Connect both computers as usual — they need to be paired.
2. On the computer that should gain a display, find the other machine in the device list and press Extend.
3. The other screen goes full-screen and starts showing your new display.
4. Press Ctrl+Alt+M to flip roles, or Stop display to end it. Closing the window on the receiving machine also ends the session.

The session survives sleep and network trouble on its own: if the connection dies unexpectedly, EasySwitch reconnects and brings the display back a couple of seconds later. If you stopped it deliberately, it stays stopped.

Which computers can do which job

Can create a display (the machine that gains the monitor)

Can show a display (the machine that becomes the monitor)

Mixed pairs are the normal case: a Linux laptop can be the monitor for your Mac, and a Mac can be the monitor for your Windows PC.

What macOS asks for the first time

The first time you extend from a Mac, macOS shows two permission prompts in a row. Both are one-time.

Screen Recording. macOS gates all screen reading behind a single permission and cannot tell “a display this app created” from “the desktop you’re using”. EasySwitch only ever reads the extra display it makes — your real screen is never captured — but the grant is still required, so the name of the permission overstates what happens. Allow it, and quit and reopen EasySwitch afterwards if the prompt appeared mid-session.

Local Network. EasySwitch has to open a connection to the other computer. Allow it.

If you allowed both and Extend still fails with a network error, it is usually macOS holding a stale permission record from an earlier version — restart the Mac, then try once more. The Setup tab in EasySwitch has a card for each grant, with a button that opens the right settings pane.

The Windows driver prompt

Windows has no built-in way for an application to add a display, so the first time you extend from a Windows machine, EasySwitch installs a signed open-source display driver. Windows shows its own installation prompt and you approve it — this happens at first use, never quietly during app install, and never with a certificate added to your trusted root store.

Quality and speed

The stream runs at up to 60 frames a second at the receiving screen’s native resolution, hardware-encoded on every operating system.

Keyboard and mouse sharing runs on its own connection, so typing and pointer movement stay sharp while a display is streaming — if the network gets tight, the video gives up bandwidth first, never your input.

When something goes wrong

The Extend button isn’t there. It appears only on connected devices, and only in builds that include the feature. Check the device shows “connected” rather than “discovered”.

It says the license doesn’t include virtual displays. Extend is part of Pro. The upgrade dialog links straight to pricing, and a key you already own can be pasted in Settings.

The other machine refuses. Its own build must be able to present a display; very old builds and X11-only environments can’t. Update both machines — they must be on the same protocol version.

“No route to host” on a Mac. macOS is blocking EasySwitch’s local network access — Extend is usually the first thing to notice, because keyboard and mouse sharing keeps working over a connection the other computer opened. Allow Local Network in Privacy & Security; if the app is already listed several times, restart the Mac and try again.

The display appears but stays black. Try stopping and starting the session; if it persists on Windows, the driver install may not have finished — extend once more and approve the prompt.

It’s smooth but the colours look soft. Text is encoded to stay sharp; large areas of flat colour compress hardest. On a Retina receiver, a Mac host sends double-resolution pixels where the encoder budget allows.