Reformatting Internal HD on 2015 MacBook Air

Select Show All Devices in Disk Utility?

View all devices or only volumes in Disk Utility on Mac - Apple Support

You will want to select the primary internal storage device. That’ll erase all associated containers and partitions.

For installing macOS, the usual reformat will be to GUID GPT partitioning with APFS.

It will help if you post a screenshot of the left panel from Disk Utility. In DU, make sure you select View > Show All Devices and open all disclosure triangles before doing the screenshot.

Unless you partitioned the drive yourself at some point, once Monterey had been installed there should be only 1 Container disk that includes two Volumes called Macintosh HD and Data, plus a Macintosh HD Snapshot.

If it is truly partitioned, you can use Disk Utility to remove each partition, one by one, starting with the last partition and working backward. For. more information, see Partition a physical disk in Disk Utility on Mac - Apple Support

zerobeat wrote:

Oh!! I had no idea that Disk Utility now "hides" the ability to select the actual mechanisms for formatting. I had been using this software for many years and never encountered this before.

This “Show All Devices” switch has been around for ~eight years; since macOS 10.13 High Sierra.

I googled this and MANY people were saying that you have to use 3rd party formatting software or terminal commands to do this.

There are no third-party formatters capable of producing Apple APFS, AFAIK.

Also probably not third-party HFS+ formatters, but I’m less certain and not going to wade around confirming that.

There are third-party tools which can create and can partition GPT, and that can erase existing storage.

There are also macOS command-line commands for formatting storage yes, but Disk Utility app works well for most.

Google search results and Google Gemini AI are, well, not my first choice in recent times.

Caution with ”MANY people are saying” is warranted too, as that can be very wrong, can be part of a scam, or can be the lead in to a joke.

Little did they know it was a simple matter of unhiding this ability that used to be there by default. Apple has been known to remove functionality from their software before (QuickTime Player is probably the most notable example, and to a lesser extent iTunes when it became Music), so I just assumed the did the same here again.

Here is the documentation for using QuickTime Player available on the current macOS 26 Tahoe version:

QuickTime Player User Guide for Mac - Apple Support

The (aggregated? accreted? amorphous?) mass that was iTunes app was split into different tools for macOS 10.15 Catalina some six years ago, including into Music, Finder, and Apple TV. Long enough ago that the “What happened to iTunes?” article itself got shelved, too. A similar split-up has more recently happened to iTunes app on Windows.

zerobeat wrote:

I googled this and MANY people were saying that you have to use 3rd party formatting software or terminal commands to do this.

FYI, you should never use third party utilities to format a drive, especially for a boot drive. Always let the OS itself partition & format the drive for its own use. Third party utilities may do something unexpected which can cause an OS to get stuck. Neither macOS or Disk Utility don't like surprises.

Little did they know it was a simple matter of unhiding this ability that used to be there by default.

FYI, you need to be very careful with AI results. The only time I look at the AI result is when I already know the topic, but just need a hint at something to help me recall what to do as it may save me loading a website with annoying ads which may take me longer to process for the information. When I look at the AI result, I see so many errors & inconsistencies with the results.....which can be very dangerous for people looking at results for a topic they don't know.

If I need to actually know the facts & understand something, then I completely ignore the AI results and click on links which I think are legitimate & relevant to my quest.

Right now, AI is way over hyped and is only useful in very small specific situations where it has been highly customized. Generic use...AI is not there & won't be for some time (if ever).