What is the ITHMB file format?
The ITHMB format was created by Apple for the iPod and iPhone with photo support. Its function is specifically defined - it stores reduced-size images, thumbnails, displayed on the screens of those devices. A single .ithmb file can hold a large number of full-colour thumbnails packed together in a proprietary binary container.
Advantages of ITHMB thumbnails
Thanks to the small size of ITHMB images, navigating between them and browsing is much faster. Thumbnails also facilitate managing and organising photos, making it easy to maintain order within the system. Browsing thumbnails requires a lower level of device resource consumption, which results in saving battery energy.
Generating ITHMB thumbnails
.ithmb files are generated automatically when images are stored in the device's memory - for example while taking photos or syncing via iTunes. The cache is maintained separately from the full-size originals; rather than embedding a direct link, the device locates each original via its internal photo database.
Details about ITHMB files
- Different
.ithmbfiles target different fixed resolutions, with the intended dimensions implied by the filename itself (for exampleF1019_1.ithmb), enabling the device to display thumbnails suited to screens of various sizes. - The
.ithmbformat stores 16-bit pixel data (typically RGB565) that is raw and uncompressed, which is why these files can reach a considerable size. - The
.ithmbformat is not common beyond the Apple environment. Because the files carry no recognised file header or magic bytes, standard image viewers cannot open them. Dedicated tools such as iThmb Converter (Windows) or File Juicer and GraphicConverter (macOS) are needed to extract thumbnails into standard formats such as .JPG or .PNG.
Security & safety
RISK: LOWITHMB is passive pixel data - it contains no code and cannot run anything, so the file itself is harmless. The real-world caution is non-malware: these are only thumbnails, so don't expect to recover full-resolution photos from them, and beware low-quality 'ITHMB viewer' download sites that bundle adware. Stick to the established extractors (iThmb Converter, File Juicer) from their official sites.
Format details
in a nutshellPrograms that open ITHMB files
Windows1 app
iThmb Converter
Paid Open the .ithmb (or point it at the device/backup folder); it slices the cache and exports each thumbnail to JPEG/PNG/BMP. Free trial, then shareware. 
macOS2 apps
GraphicConverter
Paid Open the .ithmb specifying the raw pixel geometry; GraphicConverter can read the raw thumbnail data and export to JPG/PNG. 
File Juicer
Paid Drag the .ithmb (or the whole iPod/backup) onto File Juicer; it carves out the embedded images and saves them as standard files. Technical details
deep spec| Developer | Apple |
| Container structure | Proprietary binary; individual thumbnails stored sequentially as raw pixel blocks with no per-image sub-headers |
| Pixel encoding | 16-bit RGB565 (5 bits red, 6 bits green, 5 bits blue); some device variants use UYVY for video-derived thumbnails |
| Compression | None - raw, uncompressed pixel data |
| File signature / magic bytes | No fixed magic number; format cannot be identified by header inspection alone |
| Resolution metadata | Not stored inside the file; pixel dimensions are inferred from the filename (e.g. F1019_1.ithmb encodes the thumbnail size) |
| Thumbnails per file | Hundreds of thumbnails can be packed in a single file, all sharing the same fixed pixel dimensions |
| Color depth | 16-bit (65,536 colors per pixel) |
| Byte order | Little-endian |
| MIME type | application/octet-stream (no registered IANA media type) |
| Platform scope | Apple iPod, iPhone, and iPad only; generated and consumed internally by iOS and iPodOS |
| Storage location on device | Typically iPod_Control/Artwork/ on iPod; equivalent cache directory on iPhone and iPad |
| Creation trigger | Auto-generated when photos are captured on the device or when media is synced via iTunes or Finder |
| Viewer support | Not supported by standard image viewers; requires dedicated extraction tools to slice individual thumbnails from the binary stream |
| Released | circa 2004 (iPod with photo support / Photo iPod) |
ITHMB conversions
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