Icons are a fundamental part of a graphical interface, and convey valuable information. Although QuickLook thumbnails can enhance, they can also conflict unless carefully thought out.
An old bug in UTIs can cause problems for apps, and may even crash them. The issue is that macOS can’t always tell what type of object certain ‘files’ are.
Last of 3 articles explains how macOS selects and starts the app with which to open a document which you double-clicked/tapped.
Second of 3 articles explains how macOS puts documents through its security checks before opening them.
How does macOS open the document that you double-click/tap? First of 3 parts explaining what should happen and where it can go wrong.
Additional information is now shown for UTIs, it has its own custom app icon, and works wonderfully in Dark Mode.
What to do when you need to use Uniform Type Identifiers, only to discover that Apple’s reference manual hasn’t been updated for nearly 9 years: write an app!
Telling what a file is – whether plain text, Unicode UTF-8, 32-bit code, and so on – can be hard. Just use a little magic, free in the command tool ‘file’. Includes Swift code to access magic numbers.