Unable to update my Mac to macOS Sonoma even when there is storage space available

kyrelles wrote:

I've got about 84GB left.

You do not have 84 GB left. Your hard drive is completely full.

When it comes to storage, macOS lies like a politician. When you start to get low on space, then it lies like a journalist.

You can find the truth using Disk Utility. This tool will show you how much actual free space you have. Use Disk Utility to measure your free space while you delete approximately 200 GB of large files. Don't delete any files in any hidden directories. If you want to keep any of those files, you can archive them to an external drive.

It will take a day or two until the files actually get deleted. So don't freak out when your free storage actually goes down while you delete files.

Re: "Updating Mac Os : it says I don't have enough space on my disk even though I've got about 84GB left".

Seems a Mac needs about 50Gb free at all times in order to operate smoothly, and do the tasks you give to it.

It is always a good idea to back up everything on your Mac before updating, in any case.

If needed you can always restore data from the back-up.

Eg: How to back up your Mac - Official Apple Support

or

How to: Use Time Machine to back up - Apple Support

and

Types of disks you can use with Time Machine on Mac - Apple Support

Also: how to: Free up Storage space on your Mac

There is Empty Space which can be reused by the Operating System

Then there is Purgeable Space

The two are not one and the same

Purgeable Space which is Controlled by the Operating System.

When the Operating Systems decides the computer needs additional Empty Space, it will move a portion of the Purgeable to Empty space

AFAIK - there is no User Actions to hasten this transition from Purgeable to Empty Space

It can day or longer before this will occur.

Follow the advise from @brbo and you may be able to eventually upGrade to macOS 14 Sonoma