How do I manually purge space to free up storage for software updates?

Your Mac reports 54.77 GB of available storage, of which 54.15 GB is identified as purgeable.

According to Apple, available storage includes both free storage and purgeable storage. 

Purgeable space is storage that macOS can reclaim when additional space is needed. 

Apple explains that available space can include purgeable space that macOS can free automatically by removing data such as certain caches or other items it has identified as removable. 

You cannot manually delete the items designated as purgeable through Apple's supported storage-management tools; macOS manages that process itself. (Apple Support)

It is therefore important not to interpret the 54.15 GB of purgeable storage as 54.15 GB of files that you need to locate and delete. 

Purgeable storage is a category managed by macOS, and the amount reported can change as the system determines how much space is needed.

If you want to deliberately increase the amount of free storage on the Mac, you should instead remove data that you no longer need. This can include large personal files, downloads, applications, media, backups, or other data. 

You can also move large files or libraries to an external drive if you want to keep them without storing them on the Mac.

When you delete files, the storage they occupy is not released until you empty the Trash. Once the Trash is emptied, that space becomes available as free storage. Deleting a file does not simply convert the file's storage into purgeable storage; it releases the space as free storage. (Apple Support)

Apple provides tools for identifying files and other data that are taking up storage, along with instructions for deleting items you no longer need. (Apple Support)

If the reason for investigating the storage is that a macOS update is reporting insufficient space, Apple specifically recommends starting the Mac in Safe Mode in some circumstances.

Safe Mode clears certain system caches, which can temporarily make additional storage available. These caches can be recreated by macOS as needed, so Safe Mode should be regarded as a troubleshooting measure rather than a way to permanently eliminate purgeable storage. (Apple Support)

If the update continues to fail, Apple also recommends additional troubleshooting steps depending on the error, including checking the Internet connection, attempting the installation from macOS Recovery, and using Disk Utility from Recovery to check or repair the startup disk. (Apple Support)

In summary: the 54.15 GB of purgeable storage does not need to be manually purged. macOS is responsible for managing that space and reclaiming it when necessary. If you need to create additional free space yourself, delete or move data you no longer need and empty the Trash.

If the issue is specifically an inability to install a macOS update despite having substantial purgeable space, Safe Mode and Apple's other recommended installation troubleshooting steps are the appropriate next measures.

ts1722 wrote:

My computer has 54.77 GB of available space, with 54.15 GB purgeable. Not a lot of free space

Indeed. You appear to have 62 MB of free storage.

it should be sufficient for simple software updates.

You are at risk for catastrophic data loss.

How can I manually purge the purgeable files to free up space?

Forget purgeable files. They aren't purgeable by you. The operating system will delete them if it thinks you need the space. And as you can clearly see, the operating system is very, very bad at this.

You will need to manually delete some files - a very large number of files. You should have 50 GB free at a bare minimum - ideally 100 GB free.

(Please note the units here. You currently have 62 MB free. You need 1000 times more free storage than that.)

If I delete files, will this actually create free space or will it merely create additional purgeable space?

Since you're almost to the point of system failure, it's going to be difficult. Normally, when people get very low in free storage (only about 200 times more free storage than you have), they notice that as they delete files, their free storage decreases. It's a long story, but it's a side effect of the operating system's (mis)management of storage.

I don't know what's going to happen in your case. You don't even have enough free storage to create a new snapshot. Do what you can.

Use Disk Utility to see what your actual free storage amount is. Ignore anything that says "available". That's a fantasy.

Some of the purgeable space is made of the APFS snapshots from Time Machine. You can choose to delete them to recover some of that space: Delete an APFS snapshot.

The permanent cure:-

Buy, borrow or steal an external plugin drive and copy over all your large files/folders - videos, photos, music etc.

Then drag all those old files/folders on your computer into the trash and delete it.

Going forward keep all your large files/folders on the external.

It doesn't really matter what the external drive is, USB-3.0 or USB-C will be fine for your needs and they can be either HDDs (cheaper) or SSDs.

Time Machine may be in the process of creating a new snapshot. Try to delete the older ones first.

Please note that the Time Machine snapshots shouldn't be older than 24 hours. macOS removes them automatically after that duration but sometimes some snapshots don't get purged. Don't hesitate to remove them as well.

50GB of free space is still somewhat boarder line for the smooth operation of macOS and MS.

You should really try to maintain somewhere between 80-100GB of free space for smooth trouble free operation.

Free up storage space on Mac - Apple Support

To gain larger chunks of free space, you can move your Photos, Music or Movie Libraries to an external hard drive.

Move your Photos library to save space on your Mac - Apple Support

Change where your music files are stored on Mac - Apple Support

Move Logic Pro for Mac and MainStage content - Apple Support

Move your iMovie for Mac library - Apple Support

Move a Final Cut Pro library - Apple Support

System Data is the issue ?

Reducing System/Volume/Data is a very common question. 

Part 1 of 2

Detailed methods that may or may not work 

A -  System data taking too much in MacOS Sono… - Apple Community

B - Time Machine Local Snapshot won't delete - Apple Community

C - Over 60% storage blocked by System Data - Apple Community

D - Running out of storage - system data is huge after upgrade to macOS Tahoe 26.2

E - System Data consuming storage on Mac and how to clear it

F - System Data at 114 GB AFTER deleting other files....

G - How to free up System Data space on Mac

Use another application to see where space is being used DaisyDisk 

View APFS snapshots in Disk Utility on Mac

Stop Chrome Browser From Downloading a Hidden 4GB AI File

From a fellow contributor How to Use Finder to Clear “System Data" … - Apple Community

Suggest getting an External SSD Drive and start moving your Pictures, Videos, Music and any other large files you have control over, OFF the Internal drive and Onto the External

Part 2 of 2

Quick Fix ?

For Apple Silicon computers, use Disk Utility to erase a Mac. 

Use the Erase All Content and Settings feature to quickly and securely erase all settings, data, and apps, while maintaining the operating system currently installed

For Apple Intel computers, use Disk Utility to erase an Intel-based Mac, then reinstall macOS.

Always make a Time Machine backup before proceeding.

Migrate only the user account, not the entire system.

Reinstall only the necessary applications from the Apple App Store or directly from the developers.

On Amazon Seagate and Toshiba sell 2 TB USB HDDs for £95 and 4 TB ones for £120.

This is nearly twice the price they were a year ago (thanks to demands from AI Data centres) but they are still reasonable value.

You can get 1 TB ones but you will only save £10. The 4 TB ones appear to be best value . . . most bangs for your buck.

That is correct: leave the Time Machine drive alone. The snapshots are on your own internal drive under Macintosh HD - Data in the Disk Utility app.

That's great news. I'm glad you got it sorted and were able to install the updates.

To be fare and balanced

There were a number of good trouble shooting tips