I recently accidentally deleted some system files of macOS and thus, reinstalled macOS Big Sur in recovery mode. I have been assured that any data will not be lost, but I am wondering what exactly comes under ‘data’.

I assume it means files, apps etc. but what about things like my preferences for various apps and changes I made in system preferences? Or, my saved passwords in safari? Does that come under ‘data’?

Also, if possible, could you provide what exactly will be lost/ changed and what will not.

Note: Before my re-install, I was running the latest version of macOS I.e 11.4

  • Every single build of macOS installs different files. I don’t think Apple catalogs it, but the user home folders don’t change and there are migration scripts to transform some data in the library after the packages change. Is this the sort of answer you seek? Also, the latest version of MacOS is about 4 beta builds, so if you can be specific with exact versions that helps an expert weigh in.
    – bmike
    Jun 27 at 15:28
  • 1
    Basically, I just want to know if any of my preferences/ settings and any other changes done by me will be lost? Jun 27 at 15:30
  • Very nice edit & clarification . I get what you are asking I think much better now.
    – bmike
    Jun 27 at 15:52

All the things you list are user data and settings that the macOS upgrade and update and reinstalllation process will leave alone.

Time Machine has a compare feature where you could generate a delta between what is on disk and what the last backup interval saved.

Basically, Data is what you did to change the stock Mac so files, pictures, apps you install and all the settings like time zone, Siri, sleep settings and more are all considered user data and not the system.

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