For the last 10 years, macOS has relied on Uniform Type Identifiers to recognise different types of files, for opening in apps, QuickLook, Spotlight and in other features.
UTI
Four little utilities now compatible with macOS Tahoes, covering repair of Finder aliases, creating test sparse files and checking special file types, looking up UTI types, and analysing language.
How to discover which QuickLook generator or app extension should be creating Thumbnails or Previews for different file types, using this new version of Mints.
Details of the chain of information, from the UTI of the file to be opened, through LaunchServices’ database of document types. How to deal with problems.
What if, when you double-click a document, the wrong app tries to open it, or maybe the right app but wrong version? Includes command tool use.
How does the Finder know the right app to open a file with? Or QuickLook how to preview its contents? Or other services like Spotlight know how to index and handle files? UTIs.
In Big Sur and Monterey, if you’ve not opened an app’s Help book, the first time you do it may appear empty, or simply not work. Here’s why and how to fix it.
Many think that a file’s type is determined by its extension. Although partly true, that’s indirect: it’s the UTI which sets the type, as explained here.
Explaining inodes, names, dates, permissions, file types, and specialised attributes used for iCloud.
Explore UTIs, MIME and file types, extensions, and more. Now runs native on Intel and Apple Silicon Macs.
The Eclectic Light Company 