Macbooks and Multiple Monitors

Apple Support – Mac Documentation

Here, you can find Technical Specifications for many Macs, including

MacBook Air (13-inch, M3, 2024) - Tech Specs - Apple Support

MacBook Air (15-inch, M3, 2024) - Tech Specs - Apple Support

MacBook Pro (14-inch, M4, 2024) - Tech Specs - Apple Support

MacBook Pro (14-inch, M4 Pro or M4 Max, 2024) Manuals and Downloads - Apple Support

As a rule, 13" and 15" MacBook Airs with the same chip have the same external display support. Likewise for 14" and 16" MacBook Pros with the same chip. Display support on any Apple Silicon Mac depends very heavily upon the processor chip inside, and if you adjust for the presence or absence of a built-in display, the limits on external displays tend to be very consistent across all chassis (notebook or desktop) that use a particular chip.

For both the M3 MacBook Air and base M4 MacBook Pro, you must close the lid to use two external displays (meaning you also need an external keyboard, trackpad/mouse, and to be connected to power, which could be provided by a USB-C/Thunderbolt display).

You can directly connect them or use a dock (check the specs of the dock carefully for Mac use, some PC-aimed docks use MST or DisplayLink for multiple displays, you don't want those).

If you want to drive two displays with the laptop open, you need an M3 or M4 Pro chip at a minimum.

Mac notebooks based on plain M1 and M2 chips are limited to one display, period.

Mac notebooks based on plain M3 chips can drive two external displays, but only when their lids are closed, and only with a 5K limit on the "lid closed" display that translates into fewer Retina options for a second 4K one.

A 14" MacBook Pro with a plain M4 chip can drive up to two external displays with the lid open: a first for any Mac notebook with a plain M-series chip.

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The M3 MacBook Airs have two multi-purpose USB-C (USB, USB4, DisplayPort, Thunderbolt, Charging) ports, and a MagSafe 3 charging port, that you must use for pretty much everything. Without a Thunderbolt hub or dock, you will not be able to plug two regular (non-Thunderbolt) displays into the same USB-C port. Both ports will be in use, so you will be forced to rely on a plain USB-C hub/dock, or on hub ports on USB-C monitors themselves.

14" MacBook Pros with plain M4 chips have three multi-purpose USB-C ports, a HDMI port, a SDXC card slot, and a MagSafe 3 charging port. (The third Thunderbolt port is a first for any Mac with a plain M-series chip.). So there are four places that you can use to plug in the two displays, and even if you use USB-C for both displays, you would still have one of the multi-purpose USB-C ports open for other stuff. If you connected one display via HDMI, you would have two of the three USB-C ports open.

neuroanatomist wrote:

You can directly connect them or use a dock (check the specs of the dock carefully for Mac use, some PC-aimed docks use MST or DisplayLink for multiple displays, you don't want those).

For Macs, the rules seem to be as follows:

• You can only drive one display in a hardware-supported fashion from a plain USB-C dock.

• With a Thunderbolt dock, you can drive up to two displays with resolutions of up to 4K @ 60 Hz in a hardware-supported way, or a single display with a resolution of 5K or 6K in a hardware-supported way.

• Whether you use a USB-C dock, a Thunderbolt dock, or no dock at all, you cannot use DisplayPort MST daisy-chaining, even with low-resolution monitors, or monitors that support Display Stream Compression. AFAIK, the HDMI standards don't support daisy-chaining as an option at all, so that is also right out.

Thanks for the correction about the base M4 supporting two displays with the lip open!