Dell Thunderbolt Dock WD22TB4 - Compatibility with MacBook Air M4

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Dell Thunderbolt Dock WD22TB4 - Compatibility with MacBook Air M4

Hello everyone.

A bit of context - For the longest time, I used a DisplayLink dongle to support the second monitor with my MBA M2, such that one monitor was directly connected through HDMI and the other one was connected through a CableCreation DisplayLink HDMI to USB-A connector. Both of these were then connected to my MBA M2 through an HP G-5 USB-C docking station. This worked fine, but had a cap at a 2K resolution. But I recently bought two LG Ultrafine US500 4K displays. The one connected directly through HDMI could output 4K on MBA M2 but the other one (through DisplayLink) got capped at 2K and also the image quality was subpar.

To overcome this issue, I upgraded my M2 to a MBA M4, with a hope that both monitors will now natively support 4K through the HP G5 dock. Connected them through DisplayPort 1.4 to the dock, and the dock to the M4. To my disappointment, the displays are now mirrored (though in 4K). Reading through the forum gives me a sense that this is because the HP G5 dock (the one I have from 4 years ago) is a USB C dock, and can not support two 4K displays on Mac. For that I am told I will need a thunderbolt dock.

I can go ahead and get the dock, but am unsure if that will work too. So, I am turning to this forum for guidance. Here is my expected setup after the dock upgrade -

MacBook Air M4
LG Ultrafine US500 4K displays x 2 connected through DisplayPort 1.4 ports.
Dell Thunderbolt Dock WD22TB4 (has DisplayPort compatibility and is also titled as a Thunderbolt dock).

My specific question is - will the displays connected through the DisplayPort 1.4 ports with the said dock, which is then connected to MBA M4, be able to output 4K in an extended mode as desired? Or will I need to connect these monitors specifically on the dock's thunderbolt ports through converter cables for that to work (since these displays do not have thunderbolt input ports - they only have 2 DisplayPort 1.4 and one HDMI ports each).

I want to do this right, because otherwise I feel I unnecessarily upgraded from M2.

Thank you for going through this long thread and any inputs you may have.

MacBook Air 13″, macOS 15.4

Posted on May 7, 2025 4:53 AM

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Answer 1

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Servant of Cats

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38,501 points

May 7, 2025 12:06 PM in response to suvid12

suvid12 wrote:

My specific question is - will the displays connected through the DisplayPort 1.4 ports with the said dock, which is then connected to MBA M4, be able to output 4K in an extended mode as desired?

Just found this: How to use a Dell Thunderbolt Dock WD19TB… - Apple Community, which has a link to a support article on Dell's site.

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Dell – Dell Thunderbolt Docks and Apple USB-C Hosts.

"The displays are mirrored if both the monitors are connected using the DisplayPort on the dock (that is, DP and HDMI (or) DP and DP (or) DP and USB-C)"

Or will I need to connect these monitors specifically on the dock's thunderbolt ports through converter cables for that to work (since these displays do not have thunderbolt input ports - they only have 2 DisplayPort 1.4 and one HDMI ports each).

You'd need to connect at least one monitor that way. That's not a big deal. I'd still recommend going with a dock or hub from a more Mac-oriented vendor.

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Answer 2

May 7, 2025 11:53 AM in response to suvid12

I would avoid the Dell Thunderbolt Dock WD22TB4 if I were you. It is a Thunderbolt dock, but

It has four video outputs. Macs support driving a maximum of two displays over Thunderbolt. I'm pretty sure that means that when you use that dock with a Mac, some of the outputs just "mirror" each other (because in effect, they are being fed copies of a single video signal). Then you have to figure out which pairs of display outputs, if any, will actually provide separate video signals to your two displays.
When it comes to docking stations, I don't believe supporting Mac users is high on Dell's list. (Certainly not compared with the level of support I see from more Mac-oriented vendors!).

My advice would be to look at Thunderbolt hubs, docks, and dual-display adapters from these vendors:

I have no personal experience with their Thunderbolt products, but all three have supplied Thunderbolt gear to Macintosh users for many years.

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The specifications for that monitor seem to indicate that it is a 27" monitor with 3840x2160 (UHD 4K) resolution, support for 10-bit-per-channel color, a 60 Hz refresh rate, a DisplayPort input, and a HDMI input.

If you want to connect both monitors via DisplayPort, look for

Dedicated DisplayPort ports
Thunderbolt hub ports where you can plug in USB-C to DisplayPort adapters
Thunderbolt daisy-chaining ports where you can plug in USB-C to DisplayPort adapters

Limiting yourself to products that have two dedicated DisplayPorts may severely narrow your choices, and even lead you right back towards docks that allow connecting more than two displays. Then you might face the same issue (which pairs of ports run off different signals?) as with the Dell dock.

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Dell Thunderbolt Dock WD22TB4 - Compatibility with MacBook Air M4

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