Apple has long made it a point of pride that it’s easy to add monitors for mirroring or extending the desktop to Macs. But with the multiplication of model types and limitations, you might feel stymied when you’re ready to plug your Mac with USB-C connectors that support USB 3 or 4 and Thunderbolt 3 or 4 into external displays.

Let’s start with device limitations and then move into adapters.

Apple allows Intel Macs with USB-C to support one, two, or four 4K monitors plus one additional; or if there’s an HDMI port, as on the Mac mini, one via Thunderbolt 3 or USB-C and one via HDMI. That works out as follows:

Those numbers change for 5K or 6K monitors on Macs that can handle two or more 4K displays over Thunderbolt 3. Usually, you halve the number of 4K displays to get the maximum number of 5K or 6K monitors you can attach.

Basic M1 Macs have significant display limits:

Even if you attach a Thunderbolt 3 dock with multiple display connections, you still cannot drive more than one external display over USB 4/Thunderbolt 3 on any of these devices. (But see “Extend with DisplayLink” below.)

The M1 Pro and M1 Max chips announced Oct. 18, 2021, give new MacBook Pro models expanded options. All models have three USB 4/Thunderbolt 4 ports and one HDMI port. The chip is what makes the difference for external displays:

All 6K support is up to 60 Hz and over a billion colors.

Fortunately, both USB-C and HDMI connectors require little extra effort or expense (sometimes at zero expense) to connect to displays.

One complexity you might find on certain models, particularly in the Intel generations, is that you are already using all your Thunderbolt 3 ports for power and displays or other purposes, and thus need additional USB-C connections to add monitors. In that case, a mini-dock or full-sized dock with multiple HDMI connections is the best bet.

One inexpensive option is the OWC Thunderbolt 3 mini Dock, which I reviewed last October, and which sports pass-through power up to 85 watts and has two HDMI ports for 4K displays.

Synaptic’s DisplayLink technology allows connecting additional displays via USB to Macs, PCs, and other devices. The company licenses it to third parties and releases driver support for macOS, Windows, and other operating systems.

An updated driver in February 2021 supports M1 Macs running macOS 11 Big Sur, allowing M1 Macs to expand beyond Apple’s hardware limitations. Updates later in 2021 added support for the beta releases of macOS 12 Monterey; the latest release was at the end of August 2021. (I assume this driver will support MacBook Pros with an M1 Pro and M1 Max processor, or be updated if required.)

There are a host of different adapters and docks available, plus some monitors with DisplayLink built-in. Many DisplayLink devices only list support for Windows support, but they also offer a macOS driver download. Read reviews to ensure how a given adapter or dock works with Macs in general and the release of macOS you’re running.

If you opt for DisplayLink, consider that you may need to delay upgrading to Monterey if there are any compatibility issues between the production release of that upcoming macOS update and the current state of DisplayLink drivers.

All the adapters listed on Synaptics’s products page show a USB 3 Type-A connector, but these can be connector via an adapter to USB-C or through a dock that has Type-A connectors. Some docks that incorporate DisplayLink have USB-C connectors.

This Mac 911 article is in response to a question submitted by Macworld reader Jason.

We’ve compiled a list of the questions we get asked most frequently, along with answers and links to columns: read our super FAQ to see if your question is covered. If not, we’re always looking for new problems to solve! Email yours to mac911@macworld.com, including screen captures as appropriate and whether you want your full name used. Not every question will be answered, we don’t reply to email, and we cannot provide direct troubleshooting advice.

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Glenn Fleishman’s most recent books include Take Control of Untangling Connections, Take Control of Your M-Series Mac, and Take Control of Securing Your Mac. In his spare time, he writes about printing and type history. He’s a senior contributor to Macworld, where he writes Mac 911.

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