Boot Camp says "Not enough space on startup disk"

It is possible that there is not enough free space in a single congruent area on your SSD - meaning that fragmentation is keeping you from being able to partition.

In that case, you can either try to find a utility that will defrag, or back up to another drive, reformat, partition, then restore.

I'd also advise this may be a good time to move to a larger drive.

I have the same Problem, because when i look in detail on my disk space it says 90 GB free, but there is a lot of "purgeable" space in this 90 GB that is blocking too much of my entire ssd space and i don't know how to delete it. So Boot Camp says not enough free space....

This thread shared an answer that works for me:

https://forums.developer.apple.com/thread/50126

jjasonSep 26, 2016 1:33 AM(

in response to JulianDik)

I simply opened Time Machine Preferences, clicked the Lock Icon to unlock and make changes. Then I unchecked the box next to Back Up Automatically under the TM Icon. Finally I restarted my Mac. When I turned my Mac back on to check the storage all the purgeable data was gone which freed up over 70 GB on my SSD. Afterwards I went back into the TM preferences and rechecked the Back Up Automatically box. After restarting my computer a second time I saw that the purgeable data was still gone.

This fixed my problem!! I was trying to clear my Purgeable space, so these are the steps:

• Go to System Preferences
• iCloud
• "Options" in iCloud Drive
• Deactivate "Optimize Mac Storage"
• Then go back to System Preferences
• Time Machine
• Uncheck "Back Up Automatically"
• Restart your computer, and it should be cleared 🙂

The issue is that the "OSXRESERVED" partition, that is created as part of the bootcamp process, is only 8GB in size. The drivers and ISO files need to save in this partition during the process and the 8GB is no longer enough to accommodate these files.

The fix:

1. Download your desired windows ISO.
2. Run the boot camp assistant and download the drivers from the "Action" menu.
3. Run the boot camp assistant again, but quit when you see "copying files" on the progress bar. The partitions should be made by this time and it is now trying to copy the files to OSXRESERVED.
4. Run disk utility, highlight OSXRESERVED and click Partition. Highlight the OSXRESERVED wedge and click "-" to remove it. Now click the "+" and create a new 16GB (or whatever size you need) partition named OSXRESERVED, set it to ExFAT format, and hit OK. The OSXRESERVED partition should mount itself.
5. Copy and paste the contents of the drivers folder into the OSXRESERVED partition (should be 2 folders and a file if memory serves correct). Not open the ISO and copy the files from it into OSXRESERVED as well.
6. In disk utility, right click the greyed out "bootcap" drive in the "internal" list and "Mount" it.
7. Restart your computer and hold "option/alt" during startup to bring up the boot disk menu. Select the "Windows" disk and hit enter.
8. You should now be at the windows install menu. Go through until you get to the disk select menu. Select the "bootcamp" partition, hit format, and then next.

From here you should be able to follow the prompts until the computer reboots to windows.

I had the same problem. Mine complained I did not have enough space, need 42GB. I had 45, then 50, cleaned more and more, eventually it worked after deleting lots of stuff. In total about double the space it says you need. So, you need about 90-95GB to get the go-ahead.

Hidden system files might be using more space than shown or you might have large files cluttering your Mac.

Try this to free up space:

1. Check "Storage" details in "About This Mac."
2. Clean up unused files, Downloads, and media.
3. Optimize storage with built-in macOS tools.
4. Empty Trash securely.

Why do you need to experiment with installing a different os at first place?