I have just updated to 10.9.2 and after the installation reboot this little message shows up:

Optimizing Your Mac

What exactly is happening in the background here?

2 Answers 2


Here's how I would determine what's running when you see messages like that:

  • Check the battery icon if you have a portable.
  • Check if Spotlight has queued a large reindex from spotlight
  • Check Activity Monitor - look in the Energy tab and sort on Avg Energy Impact descending

Spotlight Reindexing Progress


It's Spotlight reindexing. The same notification appears after OS X 10.8.x → 10.9 update, as well as after all 10.9.x updates so far.

  • As it occurs hours ago, I can't find the corresponding lines, any clue ? Commented Feb 26, 2014 at 17:02
  • @Samoth I can't remember what the line is that's printed to the log, but I think it was only one line so it might be hard to find. Try searching for "Spotlight"/"mdutil"/etc
    – grg
    Commented Feb 26, 2014 at 17:05
  • It would be easy to see what processes are running in the energy usage portion of Activity Monitor. I haven't picked apart the post install script for this update, but presumably we could inspect the steps there and also conclude more rigorously that it's Spotlight. It could be several things additionally like a Mail reindex or disabling known incompatible launch agents / daemons as well.
    – bmike
    Commented Feb 26, 2014 at 20:04
  • @bmike As far as I know, incompatible launch daemons are moved before this optimising takes place. When I have some spare time I'll go through the post install script and add anything I find to this answer.
    – grg
    Commented Feb 26, 2014 at 20:07
  • Things are different on 10.9.2 - Much of the post installation takes place after the reboot and the new code is running. Please post what you find. The OS keeps getting layers upon layers and it's fascinating to learn where so as to possibly guess why. Also, I've done about 40 updates on 10.9 and never once seen that pop up. It might be present on 10.8 and 10.9, but it's not visible on all computers by any stretch.
    – bmike
    Commented Feb 26, 2014 at 20:13

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