We are often asked which HDMI splitter can be used to operate 2 monitors on one PC at the same time. In principle, this works with any of our HDMI splitters or HDMI matrix switches. Both screens display the same image. In the PC world, this is called " mirroring ". But what will never work is the use of an " extended desktop ". In such a dual-monitor work environment, each monitor shows a different part of the desktop menu. The work surface is double size - a great thing. Unfortunately, this cannot be achieved with just one HDMI output on the computer, and no splitter will help. Because the splitter only distributes the incoming signal and always delivers the same picture at its outputs.
But how else does it work? There are numerous installations with 2 screens that show a different image. That's because an HDMI connection doesn't support the necessary "Multi-Stream-Transport" (MST). Only DisplayPort and USB-C "Alternate Mode" or "Thunderbolt" connections on the computer can do this. It is therefore only possible to display an extended desktop via HDMI if the graphics card already has 2 HDMI outputs. Or a DisplayPort connector that supports MST. The USB-C port is a piñata. You have to look at the documentation to see which functions are supported. Often no monitor can be operated on the USB-C port, and sometimes only one. On Apple MacBooks, MST only works over Thunderbolt.
The dual monitor function cannot be retrofitted to a computer with only one HDMI output using an HDMI splitter. The only option with such a PC is to use an external USB graphics card, which then offers 2 video outputs. The video performance of such solutions is rather low.