I have 2 Macs:

  • MacBook Air (13-inch, Early 2015), 128 GB
  • MacBook Pro (15-inch, Early 2009), 512 GB

Both of them make backups to the same Time Machine (set up on a local NAS).
My issue is that MacBook Air generates large backups almost every time it connects to Time Machine - by "large" I mean over 1 GB, often several GB.

This seems unusual to me because, to my knowledge, I don't generate large files or large number of changes on it - I use it for general office work: typically email, calendar, some work with MS Office (Word, PowerPoint, Excel), browsing.

The other Mac (MBP) is used for similar tasks, maybe a little less intensively and it backs up more frequently (typically every day vs. every couple of days) but it generates significantly smaller backups, at least by order of magnitude.

The other difference between those 2 Macs that may play a role is the macOS, but both of them have highest version of the system available for given hardware.

How I can reduce the size of backups generated by my MacBook Air? If this is more or less normal behavior, please let me know as well.

  • There is a missing component - which version of macOS are you using. "The latest version" is not a concrete statement; if Apple releases an update tomorrow, it's no longer correct. Please tell us exactly what versions you are using on which Macs. – Allan Feb 5 '19 at 22:12
  • Fair point. For Air I use Mojave, version: 10.14.2 (18C54). For Pro - I have to check the exact version later, but I believe it is El Capitan – Michal Pakula Feb 6 '19 at 8:44

This utility can show you what has been included in the last backup: BackupLoupe

If some things are being backed up that don't ever need to be, then you can add them to the exclusions list in the Time Machine Preferences section when you click the [Options] button.

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  • Thanks, this sounds very promising! I'll check it out later on, once I have access to my TimeMachine. – Michal Pakula Feb 6 '19 at 8:54
  • 3
    Thanks again for the hint. By the way, I found an alternative tool: TimeTracker. It is very basic, but it does what I need (shows the size of particular backup elements) and is for free – Michal Pakula Feb 8 '19 at 12:44
  • TimeTracker can be downloaded from charlessoft.com - The official website was harder than usual to find on Google. – TheKarateKid Oct 11 at 1:40

Do you backup your iPhone or iPad to your Mac? You can check in iTunes > Preferences > Devices to see if backups are being stored.

Time Machine generally does exactly what is needed, and attempts to modify its behaviour (beyond merely excluding items from the backup) don't end well. It also 'thins' backups after a while, so it may recover space that had previously been used.

Usual recommendations are that the backup volume should be 2 or 3 times the size of the source volume.

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