InstaTech is described as 'gives you the tools to provide instant tech support with ease and efficiency. It bundles live chat with a remote control app, enabling effective communication with your customers and quick access to the problem computer' and is a Remote Desktop Tool in the Remote Work & Education category. There are more than 50 alternatives to InstaTech for a variety of platforms, including Windows, Mac, Android, iPhone and Linux. The best alternative is TeamViewer. It's not free, so if you're looking for a free alternative, you could try Chrome Remote Desktop or DWService. Other great apps like InstaTech are AnyDesk (Paid), mRemoteNG (Free, Open Source), UltraVNC (Free, Open Source) and TightVNC (Free Personal, Open Source).
DWService is an half (only the client/agent) open source project which offers a service that allows access to remote systems (Windows, Mac, Linux, Raspberry...) using a standard web browser - without any component required on the client side.
UltraVNC is easy to use and free software that can display the screen of another computer (via the Internet or a local network) on your own screen. The program allows you to use your mouse and keyboard to control the other computer remotely.
TightVNC is a free remote desktop application. With TightVNC, you can see the desktop of a remote machine and control it with your local mouse and keyboard, just like you would do it sitting in the front of that computer.
VNC is remote access and control software which allows you to view and fully interact with one computer desktop (the "VNC Connect") using a simple program (the "VNC viewer") on another computer desktop or mobile device anywhere on the Internet.