I want to do a fresh re-installation of macOS High Sierra 10.13.6 on my computer. To do so:

  • I uninstalled all unwanted apps.
  • Backed up my computer with Time Machine.

First question

After reinstallation when I use my backup to restore my files and settings, will it restore any unwanted files such as: preferences, directories and leftovers from apps that I had deleted or will Time Machine exclude them and not transfer to my freshly reinstalled macOS?

My second question

Does Time Machine backup caches, temporary files, directories and other similar stuff, which can be generated again without any harm ?

I've been searching a lot recently but I haven't found a clear and conclusive answer.

  • 1
    You can choose if you want to restore everything or simply select folders etc Commented Aug 21, 2018 at 20:57
  • Please provide your OS version while asking a question about a mac system behaviour. It's like asking a question about mechanics, talking about a VW golf injector... Which model? Which engine?
    – Nibor Ndj
    Commented Aug 21, 2018 at 23:52
  • 1
    Welcome to Ask Different. Next time, please ask one question per question. Then link the two by commenting or pasting the link from one in the other.
    – bmike
    Commented Aug 21, 2018 at 23:59
  • @NiborNdj for this question the Mac model does not matter and I don't think the os does either
    – mmmmmm
    Commented Aug 22, 2018 at 14:39
  • @Mark I think it does, config files path can change from an OS version to the other, as well as config file contents. My metaphor with the car has a wider spectrum but I was not asking for the Mac model ;)
    – Nibor Ndj
    Commented Aug 22, 2018 at 21:16

1 Answer 1


To avoid a long and fastidious answer:

  • Time Machine is duplicating (incremental backup) your root folder, i.e. /.
  • However, you have the ability to exclude folders from the backup (see: macOS Sierra: Exclude items from a Time Machine backup
  • The answer to question 2: caches and temporary files are not backed up. They are a part of the default exclusion list of Time Machine. You can see the full exclusion list here: /System/Library/CoreServices/backupd.bundle/Contents/Resources/StdExclusions.plist.
  • The answer to question 1: Time Machine backups folders as Applications Support, Preferences. So, to be short: if you consider that removing an app == moving in the Trash folder, then you will restore all the files spread on your system by the apps you "deleted" before your last backup. If you deleted them properly by removing the .app and all the linked files spread on your system, you will end up with a clean system.

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