AlbumData.xml
This file is written out by iPhoto as a way for other applications
(such as iMovie and iDVD) to be able to easily access the contents of
your iPhoto library. You can read in more detail about this file here.
AlbumData2.xml
This file is only created by iPhoto 8. It is a smaller version of the
AlbumData.xml file that only contains information for the library's
albums and events, and none of the actual photos. This file is faster
to read for programs that only need to get the list of albums and
events in the library.
Attachments
This folder is used by iPhoto 9 as a temporary holding place for
photos that are being sent using iPhoto's built-in email features.
Auto Import
This folder is created by iPhoto 7 and later. There does not seem to
be any mention of this folder in iPhoto's documentation, but if you
put some photos into it, then quit and reopen iPhoto, it will
automatically import those photos into the iPhoto library and then
delete them from the Auto Import folder. There is also an "auto
import" Applescript command which does not appear to do anything when
called. It's not clear if this was a planned feature for iPhoto 7 that
ended up getting pulled out (but not completely, apparently), and it
doesn't seem to be very useful for anything, especially since that
folder is buried inside a package now, but that's what it does if
anyone is curious.
Backup
If a library has been upgraded from an earlier version of iPhoto to
iPhoto 9, a copy of the original database files from the library are
stored in this folder before performing the upgrade.
Caches
Only present in iPhoto 8 or later, this folder contains additional
data for the iPhoto library. Unlike some other Caches folders that can
be safe to delete, this one is not, so don't go deleting it in an
attempt to clear up disk space.
com.apple.iPhoto.plist
This file is actually not written out by iPhoto itself, but rather by
iPhoto Library Manager. It is a copy of the preferences file that is
associated with this library. When you switch between different iPhoto
libraries, iPhoto Library Manager will swap out this preference file
for the existing preferences before opening the library up.
Contents/PkgInfo
This is part of the new package structure in iPhoto 7 that gives the
package a type and creator code so that the Finder knows what
application the package belongs to.
face.db, face_blob.db
Contains the data for faces identified by the face recognition feature
added in iPhoto 8.
iLifeShared
Starting in iPhoto 9, the AlbumData2.xml file is now stored within
this folder rather than at the root level of the library package.
Info.plist
iPhoto 9 added this file, containing basic version information about
the library
iPhoto.ipspot
This file is written out by iPhoto and read in by Spotlight in order
to index the information about the photos in your photo library. You
must have iPhoto 5.0.2 or later for this file to be present.
iPhotoLock.data
This file is used by iPhoto to help prevent more than one copy of
iPhoto from accessing the library at one time.
iPod Photo Cache
This folder is created by iTunes if you choose to sync your iPhoto
library with a photo capable iPod. It contains cached information
about the last time the photos were synced and help speed up the
syncing process, allowing iTunes to tell which photos have changed
since the last sync and only update those ones. You can delete it if
you want to clear up space, but iTunes will have to create it all over
again the next time you sync your iPod's photos.
Library.data, Dir.data (iPhoto 2), Library.iPhoto, iPhoto.db (iPhoto 4, & 5), Library.iPhoto6 (iPhoto 6 & 7), iPhotoMain.db, iPhotoAux.db
(iPhoto 8), Database (iPhoto 9)
These files/folders serve as the central database where iPhoto stores
your library information. All your event, album, and photo metadata is
stored in these files.
Data, Originals, and Modified
iPhoto 6 organizes its photos fairly differently that previous
versions. Imported photos will initially be stored inside the
"Originals" folder. Within that folder, photos are organized into
subfolders based on the roll that they are in, so each roll gets its
own folder. Those rolls are then sorted by date (2006, 2005, etc.) and
put into dated folders accordingly. So, if you had a photo in a roll
named "Vacation" and dated February 24, 2004, to find that photo, go
into the "Originals" folder, then into "2004", then into the folder
named "Vacation". When you edit a photo in iPhoto, the original stays
where it is, and the edited photo is placed in the "Modified" folder,
which has the same per-roll organization scheme within it as the
"Originals" folder does. The "Data" folder contains all the scaled
down thumbnail version of photos in your library. If you upgrade to
iPhoto 6 from a previous version, iPhoto will rearrange all your
photos from the old scheme into the new scheme. After upgrading, you
may still see one or more leftover folders named "2004" and such.
These folders should no longer contain any files being used by iPhoto
6, and can be disposed of safely.
Thumbnails, Masters, and Previews
iPhoto 9 organizes photos in much the same way as iPhoto 6-8, but uses
the folder names Thumbnails, Masters, and Previews instead of Data,
Originals, and Modified
Metadata Backup
Created by iPhoto 8, containing backup copies of the metadata for your
photos, events, albums, and other library content. This information
can be used by iPhoto to recover a library whose main database has
been corrupted.
ProjectDBVersion.plist, Projects.db, Projects.db-journal, SharingActivity.db
These additional data files exist only in iPhoto 9 and contain
information relating to "keepsake" items such as books and slideshows,
and information for albums published on MobileMe, Flickr, or Facebook.
ThemeCache
A cache file used by iPhoto to store theme data used to make books,
calendars, and cards
Thumb32Segment.data, Thumb64Segment.data, ThumbJPGSegment.data
In order to improve performance, when you add photos to your library,
iPhoto creates small "thumbnail" versions of your photos and caches
them in these files. In iPhoto 5 and earlier, these files are instead
called Thumb32.data, Thumb64.data, and ThumbJPG.data.