I'm trying to associate a custom file type and extension with my Mac Catalyst app. On the Mac, I can get this to work by adding the following key/values to my Info.plist: keyCFBundleDocumentTypes/key array dict keyCFBundleTypeName/key stringCustomUTI/string keyCFBundleTypeRole/key stringEditor/string keyLSHandlerRank/key stringOwner/string keyLSItemContentTypes/key array stringcom.jnpdx.customuti/string /array /dict /array keyUTExportedTypeDeclarations/key array dict keyUTTypeConformsTo/key array stringpublic.data/string /array keyUTTypeDescription/key stringCustomUTI/string keyUTTypeIcons/key dict/ keyUTTypeIdentifier/key stringcom.jnpdx.customuti/string keyUTTypeTagSpecification/key dict keypublic.filename-extension/key array stringcustomuti/string /array keypublic.mime-type/key array stringcustom/uti/string /array /dict /dict /array Once I've modified the Info.plist, sometimes I have to build my app in Xcode and then drag the product to the Applications directory before launchd will associate the file type correctly. Once I do this, my app appears in the "Open with..." menu. However, the steps do not appear to work for a Catalyst target. If you look at the Twitter thread that I linked to before, it suggested that the Applications folder trick worked at one point, but I have had no luck getting it to work in Big Sur (I'm running 11.2.3). I've created a sample repo (including a couple of sample files) that you can try this out with so a tester can avoid the process of creating the targets. There is nothing here except for a "Hello, world!" app with the Info.plist set up as described above, with a macOS native target and a Catalyst target. (Remember the hint about dragging to Applications): https://github.com/jnpdx/MacNativeUTITest