What Is This File? Explain Unfamiliar Files from Finder on Mac

Wed, 30 Sep 2026 00:00:00 +0000

What File Is This combines a Finder Shortcut with a native result window to explain an unfamiliar file or folder in plain language.

An extension is not always enough to answer the useful questions: what produced this file, which app might open it, and is it a companion to something else? What File Is This gathers bounded local evidence through a Shortcut and displays the resulting analysis in a focused Mac window.

The project’s README currently requires macOS 27 or later. Check that requirement before downloading; this is not a tool to assume will run on every recent Mac.

Install both halves

Download the DMG from Releases, drag What File Is This into Applications, and open it once. Import What file is this?.shortcut into Shortcuts as well.

The two components have different responsibilities. The Shortcut gathers evidence and performs the analysis; the app displays its output locally. The app is not an independent file-identification engine that can generate the same result without the Shortcut.

Run it from Finder

Select one file or folder, open Finder’s contextual menu, and choose Quick Actions → What file is this?. A loading window appears while analysis is prepared.

The result can explain the likely type, associated software, ways to open it, and reasons for caution before removal. The repository’s DICOM example demonstrates the format rather than validating any medical interpretation (see Figure 1).

Figure 1: A repository example shows the explanation alongside its evidence. This is a file-format example, not a medical assessment.

Copy the result or reveal the original in Finder when you want to verify a detail. Separate runs receive separate windows; closing the final window quits the app.

Read the evidence, not just the conclusion

A file’s name, signature, metadata, nearby companions, and readable fragments can suggest its purpose. They cannot always establish which application created it or whether a project still depends on it.

An answer such as “possibly a cache” is a hypothesis. Check its location, the owning app, and any related files before deleting it. A confident explanation is also not a malware scan or a guarantee that opening a file is safe.

For example, a same-named .aae beside a photo may look disposable if you only know the extension. The neighbouring photo and its edit history suggest it could contain Apple Photos adjustments. Even then, whether you can remove it depends on whether you still need those edits.

For an archive, Archive Peek can provide another view of its contents without immediately extracting it. For media parameters, View Media Info offers a more direct metadata view.

Interface language and answer language

The app’s English/Chinese interface setting takes effect after quitting and reopening. The Shortcut’s response language is configured separately.

Open the Shortcut, find the text line $language$ = Chinese, and change the language value if needed (see Figure 2). Switching the app interface alone does not rewrite the analysis prompt.

Figure 2: The Shortcut prompt controls the response language independently of the app interface.

Read the answer in three stages

Start with a file whose origin you know but whose extension is unfamiliar, such as a camera sidecar or a configuration file from a known project. This provides a reference while you learn the result window, before investigating material with an uncertain history.

Read the explanation as three questions: what kind of file is it, what can open it, and should you keep it here? The first can be answered from format clues. The last depends on its role in your current project. A configuration file opening in a text editor does not make it a disposable note; another program may still depend on it.

When the analysis offers several possibilities, treat them as investigation leads. Reveal the item in Finder and inspect neighboring files, location, and origin. A lone download and a similarly named item inside an app’s resources can need different treatment. Returning to the folder puts the explanation back into context.

Investigate a folder without mistaking a summary for an inventory

For an unfamiliar project directory, inspect the folder first to understand its likely purpose, then examine important files individually. The Shortcut gathers bounded evidence. A summary of a large directory does not imply every file or dependency was examined.

A folder can contain source documents, generated output, and caches together. “Contains a cache” is not a reason to remove the entire project. Locate the specific subfolder and establish whether the originating software can recreate it. Keep original material, personal edits, and generated files distinguishable in Finder.

For research or specialized formats, separate file identification from content interpretation. Recognizing DICOM can help locate an appropriate viewer, but does not interpret the image. Recognizing a database does not establish that its records can be changed safely. The explanation is most useful when it points you toward a concrete next check.

Diagnose the two halves separately

If the Finder action is missing, confirm that the Shortcut was imported and configured to receive Finder Quick Action input. If it runs without opening a result window, open the installed app once and check that both components are present. Reinstalling one half may not fix a call to the other.

If the result window stays loading, return to Shortcuts and inspect which stage stopped: reading input, preparing evidence, analysis, or delivery. Try a small, readable local file to distinguish a particular-file problem from a broken workflow. Confirm that a cloud item is actually accessible too.

For mixed languages, check the correct setting: app menus come from Settings, while the analysis response comes from the Shortcut prompt. Change the prompt for an English answer under Chinese menus; quit and reopen the app when only its menus need updating. These independent controls serve different parts of the workflow.

Check the Shortcut before sensitive files

The app does not modify the selected item and displays results locally. Review the Shortcut’s evidence-gathering and analysis actions to understand what information it reads and whether an analysis service receives it.

The useful role of this workflow is to make a file easier to investigate. For deletion decisions, irreplaceable data, or specialist material, the explanation should lead you back to verifiable evidence rather than replace it. Installation and transport details are in the README.

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