/System/Volumes/Update taking up a LOT of space

The "update" volume is where macOS stages the new OS patches (aka updates) including new major versions of macOS. At some point the contents of the update volume will be the main system volume. Basically there are two macOS system volumes these days....the one you are currently booted from & using and another one which is being staged for the next update. I've never really paid attention to the low level details of how this works exactly, but once the new staged system is ready to be used, macOS may just swap them so the "update" volume retains the older system volume until the next update is installed. I have seen the "Update" volume be anywhere between 11GB to 15GB in size on average. Does not surprise me at all.

FYI, a 120GB SSD (that is what you actually have for storage with the 128GB Apple SSD) is really too small for storing more than just simple documents and a few pictures. It is embarrassing that Apple readily sold a laptop with a 120GB SSD for so long.

If 15GB of storage is a lot to you, then maybe you should consider upgrading the SSD with a larger third party OWC SSD which is a drop in replacement for the MBAir 2017.

https://eshop.macsales.com/shop/ssd/owc

You should always have at least 20GB+ free at all times for the normal operation of macOS since even 20GB can disappear quickly. Also, you need 20GB+ of Free space which is different from "Available"...macOS makes this very confusing. Check Disk Utility to get the "Free" space value. If you completely run out of free space on an APFS volume, then most likely you will need to perform a clean install since it is impossible to delete files from an APFS volume which has no free space left due to how the APFS file system works (unless Apple has built in a safety buffer which I'm not aware of).

HWTech wrote:

The "update" volume is where macOS stages the new OS patches (aka updates) including new major versions of macOS…

That doesn't explain why I have no "Macintosh HD" volume in Update on any of my Macs.

nongremlin wrote:

I was considering to upgrade the ssd and even found the adapter for using a regular m.2 drive, but I'm kinda overwhelmed by their compatibility issues (like how a WD SN550 that's in my PC won't work with my mac as far as I know)

The WD may work, but it would require an SSD adapter. The Sintech adapter appears to be the most reliable & compatible after years of reading these forums so that would be the one I would use, but there are no guarantees. I've never used an M.2 SSD internally in an Apple laptop so I have no personal experience there, although we have used a few of the OWC SSDs in our organization's Macs. Just make sure to keep the old SSD just in case it is ever needed...you may need to use it to confirm the laptop still works if (or when) you encounter an issue with a third party SSD installed internally.

Just a thought, You may want to boot into Recovery Mode and run First Aid on your drive. It may be a directory problem.

Use macOS Recovery on an Intel-based Mac - Apple Support

Here is a screen shot of one of them. The larger of the two.

FWIW, Update is not a folder, it's a Volume and you shouldn't try to clear any of it. I don't know why yours is so large. I looked at two of my Macs and Update is under 50MBs on both.

Since I don't know why yours is so large, no sorry. Maybe someone does. If you select each folder/file in Updates, what seems to be the largest?

Post a screen shot of the Update Volume in the Finder.

It looks like you're viewing the actual Library folder. Mine is 38.1 GB.

I see. I have no idea why the "Macintosh HD" volume is listed in Update. It's not in any of mine. You should wait for other replies for someone that knows how to fix the issue.

You're welcome.