macOS Ventura external monitor resolution issue

You've not provide details (e.g. which MacBook Air and exactly how are you connecting to the Dell display), but try this:

• Go to System Settings->Displays and select the Dell display (click its visual representation).

• Now hold the Control key and click on the label "Larger Text", then click on "show list". This should show a list of resolutions and an option to "Show all resolutions".

• That should show all options, and if there are any colour or refresh options you can chose "Refresh rate" near the botom of the panel.

If that doesn't work you can read this:

Dell displays have a long history of being only marginally compatible with Macs. They can generally be made to work, but configuration for optimal resolution, refresh rate and colour profile isn't always easy and there are often problems after MacOS updates.

We evaluated the U2718Q a few years ago when looking for alternative to the 23" 4k or 27" 5k LG Ultrafines, which have a significantly better, brighter display and 100% plug & play Mac compatible... but cost more and have a habit of failing soon after the warranty expires. Like the costly Apple displays, LGs require no drivers or utilities and are fully, semi-automatically configured right from System Settings-> Displays (in Ventura, formerly System Preferences-> Displays).

The U2718Q we tested (with several different iMacs & MacBooks) had a problem very similar to what you are reporting. Rather than defaulting to the best native resolution when connected to a Mac the monitor (or probably more accurately the Macs) would default to a low resolution, and many of the higher resolutions simply didn't show up as options in the Macs' display settings.

After a lot of fussing around we could get it to work, but there were problems:

• After sleep or restart the monitor would (sometimes) lose its configuration.

• Apple released a system update during our 60 day test period... and the monitor settings reverted to low res, requiring MORE troubleshooting and a different procedure to regain access to 4k.

• We had a terrible problem with coulor accuracy, e.g. green was way too strong. This was never fully resolved.

The root cause appears to be the Dell's inability to fully and correctly communicate its capabilities to the Mac. Resolving this can get complicated and may involve drivers, a special Dell or third party app, a Dell firmeare update, etc. Post more details about your configuration and perhaps someone knows the specific answer.

We just stopped using the Dell displays because the extra hassle wasn't worth the modest difference in price vs the 23" 4k LG Ultrafine designed especially for Macs.