Information about the data in a file can be found in different places: in the file’s attributes, in extended attributes that tend to be Mac-only, and embedded with the data, as in EXIF.
metadata
When Spotlight can’t find the files you expect it to, it could be that they weren’t indexed, or that Spotlight’s search has failed to find their index entries. Here’s how to tell those apart and work out what went wrong.
The Preview pane in Finder windows can show a comprehensive list of metadata, or a shortened list you can customise in Preview Options. Here’s how to use it and how it can provide further information.
They’re invisible in the Finder, even when it’s showing hidden files. They’re present in many of the folders in your Home folder. And they can do bad things like break your backups.
Apple’s several patents cast new light on how Spotlight indexes the metadata and contents of local files, and why mds and other processes need to reindex periodically.
Using the Spotlight window and Finder’s Find window to locate local files that match your search criteria. Word boundaries and their effect on search results.
Why Spotlight can now take a long time building and updating its volume indexes. Understand when forcing them to be rebuilt is a good idea, and when it isn’t.
macOS has an elaborate set of rules determining which types of xattr are preserve during different types of copying, including syncing to iCloud Drive. Here they are in full detail.
Extended attributes were added to Mac OS X 10.4, and soon supported the quarantine xattr. They have since flourished, and have valuable properties.
How the resource forks of Classic Mac OS became extended attributes in Mac OS X 10.4, then flourished. How clone files handle xattrs, and which are used by APFS itself.
The Eclectic Light Company 