All the information here was compiled by me looking at the library folder, examining the sqlite databases, monitoring changes in files, hexdumping, etc. while playing around with my personal photos collection.
Do what you want with this, but keep in mind it is unofficial and solely based on my personal observations, therefore it is incomplete and some parts could be plain wrong.
Apple may change how their software works at any time and without notice.
First stop is to navigate to your photos library which is usually located under
Pictures in your home folder
$ cd ~/Pictures/Photos \Library.photoslibrary
Depending on how old your library is and weather you’ve migrated from iPhoto or started using Photos straight away, the contents of the library might differ slightly. Some important ones are:
databaseThis is where Photos stores it’s sqlite3 databases with the most important one being
originalsYep, that’s all your original, unmodified photos in there
resourcesThis directory seems to hold information on quite a few things:
- files from your iCLoud Shared Albums, both yours and other people’s
- edited photos and editing information
- resized copies of original photos
- audit logs
- project files
- other iCloud related files
privateLooks like these are config, state and cache files. This dir also contains files related to other services in the Apple Photos ecosystem, like the
photoanalysisd(you know, the one that always eats a 100% of your CPU exactly when you are in the middle of doing some important CPU intensive work…)
Photos.sqlite database contains lots of useful information, let’s poke around. Browsing the
Z_PRIMARYKEY table reveals what I would refer to as Entities. Each record has a name, an id (
Z_SUPER which maps to the entity’s parent and some cached counters. I assume these are the various classes in Photos code.
It’s important to note the
Z_ENT for an entity, as this is used in other tables to identify the type of a record. For example, on my mac, an
Album's id is
Other tables of interest are:
ZGENERICASSETRecords in this table represent your photos
ZGENERICALBUMAlbum and folder records are stored here
Z_XXASSETSIt’s a many-to-many relationship table that links photos to albums. The
XXpart is a number that corresponds to the
Albumentity from the
Z_PRIMARYKEYtable, so in my case the name of the table is
ZADDITIONALATTRIBUTEScontains metadata about your images, like dimensions, original filename, the import session, location data, etc.
ZEXTENDEDATTRIBUTEShas some more juicy metadata, some of which seems to be pulled off of the EXIF, like aperture, shutter speed, iso, focal length, sample rate for videos, camera and lens make and model, flash info, metering mode and more location data
ZCOMPUTEDATTRIBUTESThis one seems to contain magic numbers which I assume are used internally by Photos to further classify your images, like how well you framed your shot, or if it has nice bokeh effect, etc. All some complicated AI shit.
These ATTRIBUTES tables have foreign keys that link to the corresponding photo (or asset) from the
I’ve only had a short peek at other tables, but once you get familiar with the ones mentioned above, it should be quite straightforward to navigate your way around the database if you want to explore further.
Identifying an image is done by looking it up in the
ZGENERICASSET table. For example, a photo with
D3FE5399-FA6A-47B0-976F-E7CC39EEF747 and a
ZDIRECTORY equal to
D (note that the directory name is the first character of the uuid) will be available under
D/D3FE5399-FA6A-47B0-976F-E7CC39EEF747.jpg (also look at
ZFILENAME for the exact filename including the extension).
Apple Photos does non-destructive edits to your images and original copies are kept in the
Edited copies of photos are available in the
resources/renders folder along with a
plist file for each photo (sharing the same
ZUUID) describing the edits. Edit information in these plists is base64 encoded, but decoding and hexdumping results in unreadable gibberish. I assume it’s a proprietary encoding.
Resized photo versions are available in the
resources/derivatives folder. These smaller versions include the latest edits applied to the photo.
- a medium sized version is available directly under
- a tiny version (thumbnail) is available in
To sum up, assuming we made some edits to our photo, the following files will be available to us:
- Original unmodified image:
- Image with latest edits applied:
- Smaller version with latest edits applied:
- Tiny version with latest edits applied:
_suffix may be different for you and I haven’t yet figured out how it’s generated.
NOTE 2: If there were no edits done to the original photo, then pt. 2 from the list above will not be available.
Copies of images you have shared vie Photos are made in
resources/cloudsharing. This is also where the files that have been shared by someone else are stored.
The locations structure is similar to the one for your ordinary photos:
data/YOURPERSONIDcontains folders for each shared album and inside each folder are the images for that album along with a plist file that contains the album’s name and some other metadata.
resources/derivatives/masterscontain resized versions of the images grouped in folders
YOURPERSONID folder can be obtained by reading the
Another interesting observation I made is that not all photos you share get immediately copied into the
cloudsharing directory. For example, I noticed that the copying happened on demand, e.g. when you go and actually browse the files in the Shared Album via Photos app.
Albums are recorded in
ZGENERICALBUM. I’ve noticed that this table contains records of multiple
Entity types. I tend to keep my photos quite organised and I’ve accumulated a bunch of folders with subfolders and then albums in them.
Browsing that table, it quickly becomes obvious what the fields are used for:
Z_ENTrefers to the
Entity, like a
ZTRASHEDSTATEnope, Photos doesn’t immediately delete your stuff, just marks it as deleted
ZXX_CUSTOMKEYASSETis a reference to the cover photo on your album.
XXhere again is a reference to an entity record from
ZUUIDshouldn’t need any explanation
The table describing the relationship between albums and photos/videos is
XX is again the id of your
Album entity. The
Z_XXALBUMS in this table is the foreign key to the
ZGENERICALBUM record and
Z_XXASSETS to the
XX in this case is the id of the
GenericAsset entity). What is
Z_FOK_XXASSETS? I don’t know.