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dual monitor adapter makes both external monitors mirror eachother

I have two monitors attached to my MacBook Pro 16". I bought a dual monitor adapter so I wouldn't need to use two adapters, but when I used it, both external monitors mirror each other instead of showing me 2 separate screens. When I use 2 separate adapters, one for each USB-C port, my monitors show me two separate screens like I originally wanted to have. Is there a way for me to use only one adapter or am I stuck with using two of them? I'll drop a picture of the dual adapter I was using.

MacBook Pro 16″, macOS 11.1

Posted on Jan 11, 2021 8:56 AM

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Posted on Jan 11, 2021 12:35 PM

Look at: MacBook Pro 16-inch - Technical Specifications - Apple


According to that you can have up to 4 external displays attached. However, I note the specifications also mention it has 4 USB ports so I am interpreting this as meaning you have one independent display per port. I don't know but I am guessing each port can only supply video information for a single display. That's certainly the case with the M1 line. I am guessing your adapter is just duplicating the single feed it is receiving from that port.

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Question marked as Top-ranking reply

Jan 11, 2021 12:35 PM in response to kasiakonikowski

Look at: MacBook Pro 16-inch - Technical Specifications - Apple


According to that you can have up to 4 external displays attached. However, I note the specifications also mention it has 4 USB ports so I am interpreting this as meaning you have one independent display per port. I don't know but I am guessing each port can only supply video information for a single display. That's certainly the case with the M1 line. I am guessing your adapter is just duplicating the single feed it is receiving from that port.

Jan 11, 2021 9:01 AM in response to kasiakonikowski

Which exact model MBP?


Use multiple displays with your Mac - https://support.apple.com/HT202351

"Check how many displays your Mac supports: Choose Apple () menu > About This Mac > Support, then click Specifications. On the web page that appears, the number of displays your Mac supports appears under Video Support."


In particular if this is a M1 model: "If you're using a Mac with Apple silicon, you can connect a single external display to your Mac using one of the Thunderbolt / USB 4 ports. Docks don't increase the number of displays you can connect as an extended desktop."

Jan 11, 2021 9:39 AM in response to Limnos

I have a MacBook Pro MacBook Pro (16-inch, 2019).


I am able to use the two monitors but only when I have the screens connected to two separate ports. I am able to have two separate screens to work on while also using my MacBook monitor as well. the issue comes when I connect both monitors to 1 port with the adapter, the 2 connected screens mirror each other, so whatever I pull to one monitor, it shows on the other monitor as well, but it does not mirror with my Mac. so its acting like I have only 2 separate displays on, rather than 3. this only happens when I use the dual adapter which connects to one port only.

I tried looking at the specifications, like you mentioned, but it won't open the page...

dual monitor adapter makes both external monitors mirror eachother

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