MacBook Air M3 with multiple monitors

Do not buy the MacBook Air M3 if your main driver is to be able to make use of your existing dual monitor configuration, without reading this first!

This post is about using external monitors with the M3 MacBook Air. Unlike the M1 and M2 machines which only supported one external display, the new M3 can support two external displays, with the caveat that the MacBook is put in clamshell mode, i.e the lid is closed so you can’t use it as a third screen.

I waited several years for the M3 for this feature; restricting it to one external screen in previous versions I just thought was ridiculous and it put me off buying a Mac.

The configuration I have used at my desk successfully with at least 6 different Windows laptops is

A Dell U2421E 24″ WUXGA Ultrasharp monitor with built in USB-C hub.

Laptop connected to the monitor using DisplayPort over a USB-C cable (which also provides power to the laptop)

A second monitor daisychained to the Dell via a DisplayPort cable. This is an older monitor but I used it because I find the non-widescreen format better for reading documents.

I was honestly expecting the fabled “it just works” Apple experience, and could not be more disappointed.

  1. The second display is not even detected at all by the MacBook
  2. The Dell, which produces a perfectly legible image using windows produces a slightly blurry image with the Mac.

I would fully expect that the same would occur for others who use a USB-C hub with two standard monitors connected to it.

Apple, it seems, require you to upgrade all of your equipment and are not interested in allowing you to use (or re-use – poor show on the green credentials front) your choice of monitors. From what I have subsequently found out:

  • Only Thunderbolt is fully supported for daisychaining monitors. A standard USB-C hub supporting the latest DisplayPort is not enough.
  • Only high DPI displays, i.e. 4K or above, will give you sharp text because Apple has removed a feature called sub-pixel rendering. Apparently this can be reactivated from the command line but I don’t know what the implications would be.

So, this killer feature, which isn’t really killer, just a standard expectation, is not met at all for me. If I had known, I would probably have just saved a few hundred pounds and got the M2 version which by all accounts would do exactly the same for me: one external screen.