Insufficient storage for MacOS Ventura update

ceaser161 wrote:

My MacBook Pro is saying I need an additional 23.46 GB when I have 135.2 GB of available storage. Why do I need more storage for an update

Because "available" isn't true. That's just something Apple made up. Your hard drive is completely, totally full. In theory, if it gets low enough, it might be able to recover some storage in a day or two. But regardless, you don't want to update in this condition.

Backup your data and then clean out old files. Do NOT use the System Settings > Storage. That will only confuse you. You'll need to get a 3rd party disk storage management tool where you can see where all your storage is being used. Archive the files you want to keep. Delete the ones you don't need. Be very careful with any files in any hidden "Library" folder. Deleting those files can cause unrecoverable data loss. But sometime you have to do that. Hard to say. Each case is different.

Note that after deleting all those files, you will have even less storage available. That's normal. It will take a couple of days. Ideally, you want to get to 100-200 GB of truly "free" storage. You can check this in Disk Utility. Ignore anything about "available" storage. That's fake.

In addition to @etresoft's excellent advice, I would like to point out that you need to look at the actual Free storage space. Unfortunately Apple only shows this value in two locations, although it can be calculated as well. One is within the Disk Utility app (make sure to select the "Data" volume), or within the Apple System Profiler....Disk Utility is easier to access. Ignore the "Available" value since it is very misleading.

FYI, when an APFS volume is completely out of Free storage space, then it may be impossible to delete any items to get more Free space due to how the APFS file system works and is implemented by Apple. You need to always have at least 20GB+ of Free storage space at all times...some workloads require even more Free space.

One way to recover some storage space on your boot drive is to delete the Time Machine local snapshots using Disk Utility:

I always keep the latest snapshot.