iMac 2011 not recognized as display for MacBook Air M2

rob_kell wrote:

I own a iMac (27-inch, Mid 2011 version, macOS High Sierra) that I use for photography. Since I can no longer update my iMac, I bough a MacBook Air (M2, 2023 Version) to run the program, but am looking to use the iMac as a monitor.

That won't work. Your iMac supported Target Display Mode using Thunderbolt input – but Apple later added restrictions on the video source. It must now be a Mac released in 2019 or earlier, running Catalina or earlier.

I purchased a lightningbolt 1/2 to HDMI cable, then a HDMI to usb-c cable to connect, but the MacBook/iMac is not recognizing the other.

It appears to me that what you did was to plug

• The HDMI output of a unidirectional Mini DIsplayPort (computer) to HDMI (monitor) adapter, into
• The HDMI output of a unidirectional USB-C (DisplayPort) (computer) to HDMI (monitor) adapter

No way that's going to carry a Thunderbolt signal of any sort, even if the physical connectors fit. It wouldn't have worked even if Apple had not added restrictions on the video source.

Hopefully, plugging two HDMI outputs into each other didn't fry anything.

I have tried airplay, but the Air cannot play to the iMac.

Your iMac is far too old to support being an AirPlay Receiver for AirPlay to Mac.

See: Continuity features and requirements for Apple devices - Apple Support

Would love help with this, thank you

You need a real hardware monitor.

That setup is not supported by Apple. The old iMac cannot be used as a monitor for any of the newest Macs and Target Display mode is no longer a feature of macOS, having been deprecated years ago. Apple killed target display mode hardware when the first Retina Macs were released in 2014 and the feature died in software with the release of macOS 11 Big Sur.

Please see: Use your iMac as a display with target display mode - Apple Support

Per the link above:

• Only certain older iMac models, introduced between 2009 and mid-2014, could be used as target displays and required either a Thunderbolt or Mini DisplayPort cable.
• The intended target iMac must be running macOS 10.13 High Sierra or earlier; it does not work with macOS 10.14 Mojave or later, or with Boot Camp and Windows.
• Retina display iMacs won’t work as target displays.
• In all cases the source Mac that you're connecting FROM must have been introduced in 2019 or earlier and have macOS 10.15 Catalina or earlier installed.

Please also see: Using an iMac As A Monitor (Thank you, John Galt)