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How to use your unused tablet as a second monitor

Many people have multiple monitors in their computer setups these days. However, some also have more than one computer monitor. A second monitor is typically used for tasks other than using a computer. One way to make use of a secondary monitor is to use it as a second monitor for your Android device. This can be very useful for people with multiple Android devices.

Doing so will let you keep your main monitor for gaming and internet browsing. You can also use it as an extension of your primary monitor for presentations or typing. The process is mostly easy depending on your operating system. We will give both guides for Windows and Linux. There is also an alternative way which is using a video capture adapter, we will explain that too in this article as well.

This will extend the power of your primary display without affecting its performance too much. It’s best if you choose an older model with poor battery life since it will remain charged while using as a secondary display. Using an old Android device as a secondary display is beneficial for gamers and users who prefer not to drain their primary smartphone’s battery too much while working or playing games on it simultaneously. Anyone with multiple Android devices should look into making use of this feature!

For Windows

You need to have at least an Android 5 device and at least Wİndows 10 for this process on Windows.

Get the Splashtop Wired XDisplay app from here first, both for your pc and your tablet.

And obviously setup and run the app on the Windows machine.

You will also need 15 Seconds ADB Installer and it’s drivers. You can find it here along with the guide to set it up.

Once the app is set up and you installed the proper drivers for your device, just plug in the device to PC.

And now as you can see, it’s working!

For Linux

The process is quite different on Linux machines. We used XOrg along with x11vnc server to create a virtual display then connect to it via VNC Viewer on the device. You can also do this, it’s not hard at all. To do so, follow the process below.

First of all, open a terminal and type “xrandr”. It will show you all usable display outputs along with the empty ones that are not in use. In my case, I used HDMI-1 as my main monitor was connected to HDMI-2. Though, you can do this with else outputs that are listed as well. Replace HDMI-1 with your output in the shown commands and it will work fine.

Now that we know which output to use, we will create a virtual display on that output so that we can use it on our other device. To do that, follow the commands below.

xrandr --output HDMI-1 --mode 1280x720 --right-of HDMI-2

The short explanation for this command is; We add an output to HDMI-1 output with 1280×720 resolution(you can also change that to any resolution you want to use), then defining it’s position via –right-of(you can change this to also –left-of if your device will be on left side) HDMI-2, which is my main monitor. You can also change the HDMI-2 to something else if you’re using some else output for the main display, which does show on xrandr.

Now we want to activate this display so that we can connect to it later. To do this, run the command below.

xrandr --addmode HDMI-1 1280x720

Remember, replace HDMI-1 with whatever output you used above, and replace 1280×720 with whatever resolution you have choosen above.

Now to connect to it, we need x11vnc package(as we are using XOrg for our display, you can do a research to find the required commands for Wayland though), and here’s how you can get it.

Debian based distros

sudo apt install x11vnc

Arch based distros

sudo pacman -S x11vnc

For other distros, you can make a research and see the required command to install x11vnc to your system. We also need ADB tools to forward the port over USB. just replace x11vnc with “android-tools” and run the command to install it.

Now we got x11vnc, all we need to do is start a vnc service then connect to it on our tablet. Here’s how you do it. Please note that we want to do this over USB connection to get a better stable screen output on the tablet. So you also need ADB.

adb reverse tcp:5900 tcp:5900

This will forward the port to the Android device. Now all we need to do is start the VNC service on the x11vnc.

x11vnc -clip "$hdmi-1"+0+0 -localhost -multiptr

The command output will show you which localhost to connect on the Android device. Just connect to it with a VNC viewer and you’re done! You now have your old Android device as a second screen.

Using a HDMI Video Capture Card

You can do this process with a HDMI Video Capture card as well. Refer to the video below.

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