i have Time Machine, enabled on my mac in manual mode. Each day, i making a backup by clicking "Backup Now". Each time, a few Gb are used, to do the backup.

The question is - Why so much ? Each day i change a few text files, and maybe, add several Pages documents, while don't touching anything else.

This is no more, than 10-15 Mb.

I know, that TimeMachine does not calculates differences between current and previous version of the file in question, but backs the entire file up.

What can be changed in my system so dramatically, forcing Time Machine to eat 2-3 Gb each time ?


It don't exactly know how Time Machine decides if a file needs to be backed up. But i noticed this problem. I gave TimeTracker a try (which i found via google, this post explains how it works.

I found out that Steam updated some installed games very often, so they got backed up everyday. It's also a good idea to exclude Virtual Machines and other BIG files that get changed on a regular basis. Another big factor are long logfiles that don't get rotated, my Mail folder, and other stuff you usually don't bother with.

Hint: I'm using a Time Capsule. IIRC i had to unmount it to make TimeTracker recognize my TC. The article states, that you have to mount your Time Machine backup image (it's located on the TC's Network Volume). I think you need to find out for yourself if you have a TC.


Do you have a VM/virtual hard disk on your system? Or a TrueCrypt vault? Any time you touch one file within either one, that whole container will get backed up.


This is more than likely the result of cache files from various applications. Keep in mind, Time Machine doesn't know the difference between a file you actually need and what is arguably system garbage that you could do without if you lost your hard disk.

This includes, but is not limited to: all the system logs (which grow by the second), web browsing cache, temporary files created by all your applications for whatever reason, etc. Do you download podcasts, iTunes U lectures, downloaded internet files (in ~/Downloads)? Junk accumulating on your Desktop?

You may only think about that 5 kb change to a single text file, but in that one day since your last backup, you may have accrued hundreds of megs of logs, internet cache files, podcasts, downloads and so on.

Don't worry too much though: if you delete a file from your computer it's eventually removed from the backup, too.

  • 1
    Wrong! There is an exclude list which makes time machine ignore most garbage of well written programs and system itself — run open /System/Library/CoreServices/backupd.bundle/Contents/Resources/StdExclusions.plist to view what is excluded. – tig Jul 17 '10 at 22:47
  • Wrong! The only two things I listed that are excluded by default is Safari's cache and system logs, the latter of which is of trivial size on a home computer. Furthermore, almost everything else I listed aside from system logs would be included in the backup, like Firefox's caches, which are not stored in (~)/Library/Caches but in ~/Library/Application Support. Admittedly, that is a pretty cool, so +1 for teaching me something, snark notwithstanding ;) – msanford Jul 20 '10 at 12:52

you could also try BackupLoupe. I use both this and TimeTracker. TimeTracker will (mostly) automatically mount the Time Machine drive and image (if on a remote/network drive), while with BackupLoupe you need to mount the drive first.

BackupLoupe also has a great interface for finding files backed up, as well as giving a colour-coded view of the size of backups and, as you dig down, folder by folder. It also has a much better interface for excluding files from a backup (the Apple System Preferences for TM only show up if the file / folder currently exists, but BackupLoupe will always show them.

Also, FYI, Time Machine automatically excludes certain folders, and this includes all caches that are located in standard locations, as well as temporary files.

(Note: If you are using a network drive, such as an airport disk or Time Capsule, I have noticed that with 10.6.4, manually mounting the image with Finder (which you have to do with BackupLoupe), is causing performance issues. I therefore recommend using TimeTracker to mount the image automatically, and then run BackupLoupe).

For anyone that wants to know what is being backed up and when, BackupLoupe is brilliant. It's only $5, and even then it is an honour system, so you don't need to pay if you don't really use it or like it.

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