ITHMB files and the iPod, iPhone, and iPad photo cache

What is the iTHMB file extension? How are iTHMB files generated? In the previous article about how to view iTHMB file types, it was stated that each time a photo is saved to an iPod an iTHMB file is automatically created. We'd like to take a closer look at this process.

The Ithmb(.ithmb) is a collection of small thumbnail images stored together in one file for convenient viewing (for an iTHMB view you generally need a special device).  On a PC, an iTHMB file is created when syncing an iOS device with iTunes.  The file is saved to the original device and to your PC.

iTunes creates a cache folder on the hard drive when you sync an iOS device (such as an iPod, iPhone, or iPad), to a computer (Mac or PC).  The photo cache is created to store the following:

Name and Location (iOS device):

There are several factors that determine the name and the location of the iTHMB and index files including: the iOS device type (iPod, iPhone, iPad), the iOS version of the device, and whether the iTHMB file has reached its maximum size.

More recent iOS versions automatically store the index file as “Photos.sqlite” in the mobile/Media/PhotoData/ directory and iTHMB files are stored in the “Thumbnails” subfolder.  Earlier iOS versions store the index files in the mobile/Media/Photos/ directory with the name “PhotoDatabase”.  The iTHMB files were located in the “Thumbs” subfolder.

Naming of the iTHMB files is also dependent on the iOS version.  For more recent versions the file is named using the following naming convention: AxB.ithmb (for example: “240x240.ithmb”).  Each iTHMB file can store numerous thumbnails but each image is of the same size as is reflected in the name.  Previous versions use the following: F####_#.ithmb (for example: “F3039_1.ithmb”).  A new file is created and incremented when the file has reached its maximum size.

Size:

iTHMB files can be significantly larger in size than the original files.  This is because the iTHMB file contains uncompressed graphic data.  As a result, the iTunes synchronization is faster and smoother.

Changing the Location (Mac and PC):

 iTunes automatically creates a folder called "iPod Photo Cache” when syncing photos with iPod, IPhone, or iPad.  This folder is located in the folder you select when performing the sync.   You have the option of changing the selection in the “Sync Photos From” pop-up menu.  When you perform this action the previous folder will remain and a new iPod Photo Cache folder is created.

However, if things go wrong and you want to view ithmb files easily, you may need to somehow find an ithmb converter or ithmb viewer to actually see these files.

For information on iOS backups, refer to this Apple support article: http://support.apple.com/kb/HT4946