Dual monitors

We need more information.

Is the Mac your iMac or a different Mac? What is the exact model Mac (Apple menu -> About this Mac) and give us all that information (which Mac, the year, CPU and the graphics chip) Given this information we can figure out what ports you have available, and what kind of external display (or displays) your Mac will support.

Do you want to add 1 additional monitor to work with your iMac, or are you talking about adding 2 additional (dual) monitors?

How big a monitor do you want? Do you want 1080p or a 4K monitor? Does the monitor have to work a 30Hz, 60Hz or 120Hz (users that want to monitor to play action games, what a monitor with a faster refresh rate)?

I personally have a Late 2009 27" iMac which uses a miniDisplay Port for an external monitor. I have a miniDisplay Port to DVI adapter driving a 1080p monitor. I could drive a higher density monitor, but since work provided this monitor, I do not have anything to complain about.

A more recent Mac has multiple Thunderbolt 2 or 3 ports which can support more than a single external monitor and a higher density at a faster refresh rate.

If this is a Mac mini or a Macbook Pro there will be different capabilities. That is why we need to know more about what Mac you have and what kind of external display(s) you want.

I just purchased an LCD USB monitor and my MacBook Air doesn't see it. The monitor logo lights and then goes off. What do I need to know to make it work?

https://support.displaylink.com/forums/287786-displaylink-feature-suggestions/su ggestions/33252664-macos-high-sierra-10-…

Just plug in the 2nd monitor and you should be fine! It's plug and play!

If you want to change anything specific, go to 'System Preferences', then 'Displays.'

Hope this helps,
Richard

I just purchased an LCD USB monitor and my MacBook Air doesn't see it. The monitor logo lights and then goes off. What do I need to know to make it work?

KP