Connecting iMac 24 inch 2021 Apple M1 chip to Dell 2209WA external monitor

Looks like maybe too many adapters. USB-C to HDMI > HDMI > HDMI to DVI.

Get yourself a USB-C to DVI adapter and use the Dell supplied DVI cable.

for a few example's

https://www.amazon.com/dp/B07CCKTKXV/ref=sspa_dk_detail_6?

https://www.amazon.com/Cable-Matters-Adapter-USB-C-Black/dp/B012B58JRM?

https://www.amazon.com/Thunderbolt-Adapter-Converter-Compatible-MacBook/dp/B0768RFQ83/ref=asc_df_B0768RFQ83/?

https://dl.dell.com/manuals/all-products/esuprt_electronics/esuprt_display/dell-2209wa_user's%20guide_en-us.pdf

The Dell 2209WA is a 22" monitor with 1680x1050 pixel resolution. It has DVI and VGA inputs. I concur with the recommendation to replace those daisy-chained adapters (USB-C to HDMI to DVI), either with

• A USB-C (male) to DVI (female) adapter, plus a DVI cable, or
• A USB-C (male) to DVI (male) adapter cable

Whatever adapters works to connect your 24" M1 iMac to the Dell 2209WA should also work to connect your M1 MacBook Air to the Dell 2209WA.

You could use a single adapter, and move the USB-C end of the cable as needed.

Another possibility would be to buy two adapters or adapter cables: USB-C to DVI, USB-C to VGA. Plug both into the monitor, plug one into the 24" M1 iMac, then plug or unplug the other one from the M1 MacBook Air as desired. In this scenario, you would use controls on the monitor to switch between its DVI and VGA inputs, but you wouldn't need to fiddle around behind the iMac to temporarily reassign the external monitor to the MacBook Air.

bree06 wrote:

I first was trying to use the [24" M1] imac as an external display for my 2020 M1 macbook air but apparently neither of these devices can be used as an external monitor.

Neither of them can be used as an external hardware monitor for each other – or for any other device.

Continuity features and requirements on Apple devices - Apple Support

Set up your Mac to be an AirPlay Receiver - Apple Support

If they are both running Monterey, you could set either one up to be an AirPlay Receiver – and use it as an AirPlay screen for the other one. AirPlay is not as good as a real hardware monitor connection and my understanding is that even in AirPlay v2, the choice of resolutions is quite limited.

It's possible you won't find the video quality usable at all. I certainly wouldn't buy a Mac on the basis of being able to AirPlay to it. But you already have the two Macs, so there is no cost for you to experiment with it.

Notes:

• I do not believe that an AirPlay display counts against your 24" M1 iMac's limit of one external display or against your M1 MacBook Air's limit of one external display. Those limits are for hardware-supported monitors.
• You might only be able to have one AirPlay or Sidecar display at a time. (Sidecar is a bit like AirPlay, but lets you use an iPad as a second screen and input device for a Mac.)

I can't tell from the picture what exactly is the port on the monitor?