The time came and I took the plunge to upgrade to iOS 9, so I went through my normal process of starting iTunes, making sure that all apps were updated and then proceeded to sync my iPhone and take a local backup just in case.
As I went through this process I noticed my disk space was going down quite dramatically, My C: drive is set at around 200GB which should be plenty for Windows, program files, and any application data. I did a little digging and found that iTunes saves backups of your iPhone on the hard drive somewhere, some places suggest that you delete these directly off the hard drive and others using the iTunes user interface.
I decided to take a look at the folder in question, this is located here …
[username] is the user you sign into Windows with. This contains sub-folders which seem to match the number of backups you have listed in iTunes, they have names such as this.
From inspection it looks like the last part of the folder name is the date and time of the backup, but this is unimportant.
I decided against deleting these folders directly and opted for the iTunes user interface; that’s got to be the correct way, right?. In the Windows version you select the menu item Edit ~ Preferences and then select the Devices tab.
Now it is simply a matter of selecting the backup you want to delete and pressing the Delete button, seems quite straightforward. So I proceed to delete 8 of the 10 backups that were years old, I was impressed that the delete took such a short amount of time, I just assumed that iTunes was batching up the deletes until I pressed the OK button (normal practice so you can press Cancel and nothing happens).
I press the OK button expecting it to take ages and a progress bar indicating that things are being deleted, nope, nothing, nada, it just exits, wow, Apple and iTunes is amazing to remove everything so quickly (so I thought).
Now to check the hard disk and the recycle bin, nothing in the recycle bin and no disk space has been reclaimed, strange I think, so I check the backup folder again, I can see that 8 folders have disappears and 2 are remaining, what is going on? I finally take a shot in the dark and press Windows Key+R to bring up the run dialog, type in %temp% which takes you to your temporary folder (e.g. C:\Users\[username]\AppData\Local\Temp) and low and behold there are all the folders that were deleted from the backup folder.
So all iTunes did was to move the folders from the backup folder to the temporary folder, thanks Apple, wouldn’t it have been simpler to just delete them, how many people would think of going to the temporary folder (in fact how many typical users even know that there is a temporary folder). The problem is that the temporary folder is meant to be used by applications to store temporary files that are cleaned up when the user exits the program, iTunes just dumped the folders there and even after exiting iTunes the folders were still there, very shoddy coding in my opinion.
So, the fix was to simply delete the folders from the temporary folder and voilà, 40GB of reclaimed space.