MacBook Air storage full for Monterey upgrade

It is possible to get a larger internal SSD for that Mac. This route might not be too attractive given that your Mac is limited to Monterey and that SSD prices have been going through the roof. (Even the cheapest 480 GB kit is $150, assuming that you want tools and a transfer enclosure.)

Other World Computing – OWC Solid State Drives For MacBook Air 11" & 13" (Mid 2013 - Mid 2017)

If you are interested in this, there are some important caveats:

• You must install Monterey somewhere successfully before installing a third-party SSD in your MacBook Air. The Monterey installer may try to update firmware on your Mac. If the internal SSD is a third-party SSD when it does that, the firmware update and the Monterey update will both fail.
• You need to be careful about taking anti-static precautions when handing the new SSD and working on the Mac.
• I would recommend making sure that you always have a bootable disk to fall back on at all times. If you were to wipe out all local copies of macOS, then put all your eggs in the basket of Internet Recovery, that might put you between a rock and a hard place should Internet Recovery fail.
• And as always, make sure to back up your data.

FYI, a 120GB SSD is barely large enough to run macOS before you even store any personal files on it. That is the sad truth here. These days it is important to have 80GB-100GB of Free storage space before starting any workloads since that 100GB of Free space can disappear very quickly. Older versions of macOS could get away with just a 120GB SSD, but it was always a very limited in space.

Many old MBAirs also had just 4GB of memory with 8GB of memory being the most available.....the latter is a problem, but the former is a huge hindrance and can easily cause more storage space to be consumed due to Virtual Memory (aka "Swap").

Now combine that with the macOS 12.x Monterey installer being very large due to it being a Universal app containing both Intel & Apple Silicon executable files (later versions of macOS have even larger installers). Apple's documentation mentions the Monterey installer requires at least 36GB of Free storage space when running the installer while booted into macOS (45GB if using Recovery Mode or a bootable macOS USB installer). I think those are the correct values, but I can no longer find the Apple article & I'm having trouble locating my older posts from four years ago.

Yet another complication is the very misleading "Available" storage space value shown everywhere in macOS which is not synonymous with Free. The only place you can actually see the actual Free storage space value is in Disk Utility on the right side just below the storage bar graph.

It is very hard to create Free space on SSDs which are so small. We see the same problem even with systems with larger 250GB SSDs. Once the boot drive is very low on Free storage space it is really hard to recover that storage space.

You can try booting into Safe Mode to see if that makes any difference since fewer apps & processes are running.

Before you attempt to upgrade macOS you absolutely must make a good backup of your computer to safe guard your important files just in case something goes wrong.

If you cannot free up more space on the internal drive, say, by

• Deleting stuff, or
• Copying stuff to an external drive, then deleting the copies on the internal drive

you will not be able to install Monterey "in place" on the internal drive. It is as simple as that.

You could, perhaps, install Monterey on an external drive, and leave the internal one set up with Mojave.

HWTech wrote:

Now combine that with the macOS 12.x Monterey installer being very large due to it being a Universal app containing both Intel & Apple Silicon executable files (later versions of macOS have even larger installers). Apple's documentation mentions the Monterey installer requires at least 36GB of Free storage space when running the installer while booted into macOS (45GB if using Recovery Mode or a bootable macOS USB installer). I think those are the correct values, but I can no longer find the Apple article & I'm having trouble locating my older posts from four years ago.

The article to which FoxFifth linked in the thread What free space should be available to in… - Apple Community has changed – but I'm guessing that the quote

"If upgrading from macOS Sierra or later, your Mac needs 26GB of available storage to upgrade. If upgrading from an earlier release, your Mac needs up to 44GB of available storage."

was a word-for-word quote from an Apple's Support article at that time. BDAqua then said that if it was him, he'd shoot for 20-30GB more than those numbers – and FoxFifth concurred.