Who has been using my filename extension?

How to discover which app ‘owns’ the mapping between a filename extension and its UTI, and whether you can do anything to fix a conflict.

Matching files to apps: how UTIs work

How macOS makes the association between file types and apps for the Finder and GUI, using UTIs and their associated data including filename extensions. Why clashes occur, and how they’re resolved.

What determines a file’s type?

Without the correct filename extension, macOS appears unable to associate files with apps, preview then using QuickLook, or index them for Spotlight. But there’s more to determining file types than extensions, there’s also a little magic involved.

Open a file with the right app

When you double-click a file and expect to see it opened by the app of your choice, but instead it’s opened by the wrong app, or the wrong version of the right app, or maybe macOS refuses to open it at all. How to fix that.

Last Week on My Mac: Intel Macs will be stuck with bugs

Spotlight fails to index the content of text files starting with odd characters like ‘LG’ and ‘Draw’, Although we understand this is caused by checking the file type using file(1), this suggests an explanation of why it should do that. And whether it will ever get fixed for Intel Macs.

Fun with UTIs, QuickLook and Spotlight

If generating QuickLook thumbnails and previews, and indexing metadata for Spotlight, depend on UTIs, how come they tolerate misleading file extensions? A simple practical demo.

Tackle QuickLook problems

How to discover what went wrong when a document doesn’t show the right thumbnail, but a generic icon instead. How to dive deeper to solve problems with 3rd party thumbnail and preview generators.

Providable 1.2 works on non-English systems, and why it didn’t previously

Will now list apps installed on systems running with primary languages other than English. Problems resulted from unexpected behaviour of Spotlight and search with mdfind, as explained here in detail.

Explainer: How does macOS recognise file types?

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.

More updates for Tahoe: Aliases (Alifix), special files (Sparsity), file types (UTIutility) and language (Nalaprop)

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.