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Similar to Xcode free space requirement, but different details.

We could not complete your update

There is not enough disk space available to install the product.

The download size lists:

Version 11.0 • 7.6 GB

and my Mac has 31.2 GB available according to About This Mac : Storage

My question is this: How can I discover what the exact storage requirements are for this update without performing the update? I'm looking for a definitive answer, not methods for estimation. Thanks!

EDIT: I'm not looking for sector-specific values. I'm just trying to understand how much available storage is actually required for a successful update—clearly it's not 7.6 GB.

EDIT 2: Mysteriously, Xcode now updates with no change in available storage space. In fact, it appears I have a few hundred MB less available storage than before.

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I don't think there is a definitive answer, because it's likely to depend on the specific Mac & how the data aligns to sector sizes when written. You'd see the same thing if you wrote a 1GB movie file & 1GB of small text files to a drive. The byte count may be the same, but the space used on disk would not.

If you look at the three basic ways to see how much space is left on your drive [Storage, Disk Utility & Get Info], one thing you'll notice is they don't actually agree on their definition of "free" space.

If your drive is so full that you are struggling to squeeze something on - which in itself is not a good thing, you really need to keep 10 - 20% free space, ironically more for a smaller drive - then the figure you need to be looking at is the one in Disk Utility, under the blue bar [green outline].

That is the amount of actual free space you have, including purgeable.
Purgeable data will not just get out of the way if you need the space all in one go. You need to either manually shrink local Time Machine backups, or incrementally fill the drive with junk data then erase it. If you have "Store in iCloud" set up, you need to give it time to work, whilst you do this.

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  • Thanks for responding. I've added an edit to the question to clarify that I'm not looking for a value down to the sector—I just want to know how much available storage is actually needed for the update to succeed. It's obviously not the value reported for the download size (which doesn't consider copying, decompression, etc.). – jsejcksn Sep 24 at 22:28
  • Basically, your drive is dangerously full. The fix for that is to free up enough space that you have room for Time Machine & also virtual memory. As it is you're constantly skirting the very edge of usability & are looking for some 'magic number' to make you feel better about it. Your magic number is about 15% free space, unless you only have a 128GB drive, in which case it's more. – Tetsujin Sep 26 at 17:31
  • I know I can use mkfile or pipe 0s into a temp file until I have no storage left, then delete that file to regain the used, purgeable space. That’s not my question, though. I want go know how much storage is actually required for a successful install of Xcode 11. – jsejcksn Sep 26 at 21:18
  • How long is a piece of string? – Tetsujin Sep 27 at 5:24
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There's really no easy way to produce a definite answer for you. The definite answer varies from system to system.

You could get the definitive answer by freeing a small amount of disk space. Taking a full backup of your system. Try installing. When it fails, restore from backup. Repeat until you have the definitive answer.

It would be an unrealistic amount of work to get to a number that you would then have no interest in having, as you have already installed the software.

EDIT: You have changed your question so that you no longer require a "definitive" answer, but rather want an "approximate answer". To that I can I add that my installations of Xcode are approx. 15-20 GB in size depending on what exactly is installed on each computer. Note that for updating you'll need room for both the currently installed version plus update files. You might find that it is easier on your disk space requirements to simply delete Xcode, and then reinstall it. You might get be with even less disk space if you download Xcode manually from the Apple web site instead of from the App Store.

  • Thanks for responding. I stated in the question that I want to know without having to perform the update. – jsejcksn Sep 24 at 22:26
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    @jsejcksn Yes, and I'm telling you that performing the update is the only way to know - and then I'm telling you how to revert your system to before you did that. The net result being that you get the knowledge without performing the update. There's no other way. – jksoegaard Sep 24 at 22:36

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