Virtual displays

A virtual display is a screen that exists only in software. The host treats it like a real monitor, so you can stream it and control it as usual. Two things use it:

• A second screen from the viewer. In a session, open the monitor menu and choose Add display…. The host adds a screen sized to your window and switches to it. Remove display takes it away again.
• Computers with no monitor. A Mac mini in a cupboard or a PC without a screen often has nothing to capture. With virtual displays allowed, the host adds a 1920x1080 screen for the session when you connect.

Every virtual display OpenDesk adds is removed when the session ends or the app quits. A viewer can add up to two per session.

Allow it on the host

On the host, under hosting settings on Home, tick Let viewers add virtual displays. It’s on by default. The person at the host gets a notice each time one is added.

macOS

Nothing to install. OpenDesk uses the virtual display support built into macOS.

With HiDPI the size you ask for is in points, so a display added from a Retina window may show at half its pixel size. Text stays readable either way.

Windows

Windows can’t add a screen without a display driver. OpenDesk uses the free USB Mobile Monitor driver by Amyuni, which is signed by Microsoft and is the same driver RustDesk uses.

1. On the host, with virtual displays allowed, click Install virtual display driver.
2. Read Amyuni’s licence and click Accept and install.
3. Approve the administrator prompt.

OpenDesk downloads the driver from Amyuni, checks the file against a fixed fingerprint before using it, and installs it with Windows’ own driver tools. The button changes to Uninstall once the driver is in.

Limits of the driver:

• Sizes snap to a fixed list: 1280x720, 1366x768, 1600x900, 1920x1080, 1920x1200, 2560x1440, 2560x1600, 2880x1800, 3440x1440 and 3840x2160. The monitor menu shows the size you actually got.
• At most four virtual screens on the computer, counting ones added by other apps.
• Displays come off newest first. If you try to remove an older one, OpenDesk asks you to remove the newer one first.
• Any program on that computer can add or remove the driver’s screens. See Security model.

Linux

Not supported yet. Connect a monitor, or an HDMI dummy plug (a small adapter that pretends to be a monitor).

Without a virtual display

If the host has no screen and virtual displays are off or unavailable, the viewer sees “That computer has no screen connected” with the options above. An HDMI dummy plug works on every system and needs no setup.