Understand preview and search providers
A provider is a component that tells macOS it can handle certain file types. Different components can create previews, create thumbnails, or supply information for search.
- Quick Look Preview provider (Space bar)
- Creates the larger preview you see when you select a file in Finder and press the Space bar.
- Quick Look Thumbnail provider (Finder thumbnails)
- Creates the small visual representation used for a file in Finder.
- Legacy Quick Look generators (.qlgenerator)
- An older kind of preview component. A matching declaration can be shown, but its presence does not prove that your macOS version uses it.
- Spotlight Importer Candidates
- Components that declare which file types they can extract search metadata from. These are separate from Quick Look providers.
Read a candidate match
- Confirm the inspected file’s UTI in File.
- Check the candidate’s name, identifier, and path.
- Read Matched UTI and, when shown, Matched via. “Via image” means that a more general image type supports the match.
- Open Info to inspect the provider’s declared supported UTIs. The starred supported type is the one used for the match.
For example, a provider declaring public.jpeg is a more specific match for a JPEG than one declaring only public.image. If equally specific candidates remain, the report marks the match ambiguous. It cannot determine macOS’s choice between them.
“No matching declaration” means no match was found in the inventory the app could read. Check folder access and Discovery Coverage before concluding that a component is absent.
What the results establish
The inspector reads declarations; it does not run the provider or importer to test its output. A candidate is evidence of advertised support, not a test that a particular document can be rendered successfully.
- The app cannot identify the Quick Look provider or Spotlight importer actually selected for a particular operation.
- Private registration records and user enabled/disabled or superseded state are unavailable through this app.
- A component may support types it does not advertise, or decline a particular file despite its declared type.
- Providers outside readable discovery folders can be missing from the inventory.
Technical detail: discovery and ranking
The shared inventory recursively reads accessible .appex, .qlgenerator, and .mdimporter bundles. Hidden directories and nonstandard bundle layouts are included; there is no fixed scan depth. Symbolic links that leave a selected root are excluded.
Modern Quick Look matching uses the extension’s own supported-type declarations, including QLSupportedContentTypes, preview QLSupportedFileTypes, and explicit activation-rule types. A host application’s document types alone do not establish extension support. Preview and thumbnail extension points are evaluated separately.
Exact identifiers match even when undeclared. Known conformance relationships allow broader matches; nearer and more specific supported types rank ahead of broader types. The displayed tree index describes the matching hierarchy, not a probability or measured preview success rate. Legacy generators remain separate from modern extension candidates. Importer matching uses MDImporter role declarations and their supported types.