Deskreen is a free and open source desktop app that turns any device with a web browser into a second screen for your Windows, Mac and Linux computer. It works over Wi-Fi, no need for any cable.
Additionally, you can use any device’s web browser to mirror your computer screen or view a single application window from your computer screen. The app also supports multiple screen sharing sessions to as many devices as you want along with end-to-end encryption.
Users can even have an extended desktop experience with the help of a Dummy Display Plug. Simply plug it into your computer to make it think that an external display is connected.
Get it for free from this link. Note that it comes with different versions for Windows, Mac and Linux. You don’t need to install any app on your mobile phone, tablet or other computer that you want to share the screen with. Simply use a web browser on them to access Deskreen View for web.