Occasionally when I am using iPhoto an app with a generic white Lego piece icon opens on the dock with the name "com.apple.MediaLibraryService.xpc".

Activity Monitor lists it as "(Not Responding)" and shows it using a pretty large amount of CPU time. When I quit iPhoto its % CPU drops to zero, but it remains in the dock and remains unresponsive in Activity Monitor.

It doesn't happen every time I use iPhoto, and there doesn't seem to be any particular action that triggers it to open. It does seem to correspond to a general slowing of responsiveness (already not great) in iPhoto. I am generally loathe to force quit something if I don't know what it is.

Does anyone know what this app does, why it is opening, and how to prevent it from hogging my CPU when I'm working?


The com.apple.medialibraryservice.xpc is a process used for a number of Apple-specific applications and services, including: indexing photos through iTunes (when syncing), and importing and exporting images in iPhoto.

Some users have reported that this happens when importing slo-mo videos into iPhoto from the iPhone 5s. This could be happening to you when syncing your iOS device--you can disable automatic syncing for iTunes as a temporary fix to see if helps your situation.

  • It has not happened when syncing. It happens when iTunes is not even open. Do you have a source for your description of what it is? – Robert Feb 19 '14 at 18:27

Just restart the Mac and the lego piece dissapeared

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