SpaceDesk is THE single best remote display (not RPD) app/server combo I have found, and I have tried ALOT... on my lan at home, using SpaceDesk, I was able to connect my crappy android (wifi) and a SECOND win10 machine (wired) to my primary win10 machine which already has two displays with ZERO lag, AND at max quality... my personal hardware is all old (core 2 duo's both), and the gfx cards rate VERY low also, plus my lan is still 10/100. THIS should tell you, everything you need to know about this software if you know anything about computers. if not, let me put it like this: every other app/server combo I have tried with JUST my primary and android, has TONS of lag, and were not very stable, SpaceDesk is neither. VERY smooth, VERY stable. tho, I was unable to find a keyboard, it does allow you to take control from any device connected thru it... (touch screen for mouse via android, and even the secondary machines mouse and keyboard!) I RARELY pay for software, and there are EXTREMELY few I say this about, but I would MOST def pay over $50 USD for it!

Thank you SpaceDesk !

[Edited by pratikcparmar, August 06]

I compared Spacedesk with Windows built-in Miracast. Overall, it works better unless you use a 4K screen.

Pro

• Flexible control of image quality: I can manually adjust image quality to fit in the bandwidth or keep the best quality. I can use the highest setting with a 900p screen on my 1Gb Ethernet. (It will sometimes freeze like what I write in the con below, though.) Miracast doesn't provide any settings.
• Responsive input: Input from viewer PC almost can't feel any lag in Ethernet mode. It will be a little laggy if you move the mouse from the viewer's PC when the mouse pointer is on the viewer screen because of image transfer delay. While Miracast's input from the viewer PC is very laggy and when the difference in the screen resolution is large, mouse movement will be jumpy.
• WIFI isn't a must: Miracast need WIFI to initiate the connection even in Ethernet mode.

Con

• Not optimized enough for screens with large resolution( or networks with low bandwidth): When I connected to my laptop with a 4K screen, everything was a lot worse than Miracast. I even bought a 1Gb network switch hoping it works better than Miracast but didn't. With a reasonable image quality, it couldn't achieve a smooth experience and would periodically freeze like 0.5 seconds. On the contrary, image responsiveness in Miracast is instant when gaming mode is selected (which IMH should always be selected) no matter what resolution is used. There is literally no lag. However, the overall smoothness or frame rate is lower. And Miracast performs surprisingly well in 4K. I feel the image quality is near 90/100 if in Spacedesk, with only a constant 3MB/s network traffic. While Spacedesk can take a range from 10MB/s to 40MB/s but performs worse.
• Doesn't support multi-touch: Neither does Miracast, though.

Its a great way to re purpose an old ipad/tablet and this app is the only one thats free and works relibly.

really wish linux was supported though

If you have additional tablet/ipad or laptop lying around, you can use them for additional screen. It's really sluggish though on the browser. I really wish they have Linux client, I'd paid for it.

So far this is the only application that allows you to wirelessly (or not) extend your monitor display on to another computer or laptop.
Very simple setup, and Very good instructions on its website.
The flaw is it has lags and the image quality is not too good (Unless you have a very good performance computer). It is not gonna be as good as you connect your display via HDMI or VGA cable.

BEST SOLUTION SO FAR!!!
Just click a button and the work is done! Managed to screen-share from an old computer!
Tbh I'm cùmming