With well over 400 app extensions and plugins managed by PlugInKit in Sequoia 15.4.1, this article tries to give an overview of their management and control, as well as the diversity of their functions. This follows: a general introduction an account of discovery and management by PlugInKit AppexIndexer to examine appexes known to PlugInKit Apple’s appex Home page for developers. Appex types Although Apple refers to the type identifier for appexes as NSExtensionPointIdentifier in its developer documentation, where it lists some of them, in macOS this is also synonymous with NSExtensionPointName. In pluginkit dumps, it’s referred to as the SDK, and LaunchServices dumps use both terms, NSExtensionPointName in NSExtensionsAttributes, and NSExtensionPointIdentifier in NSExtension. This is even more confused in the log, where PlugInKit’s entries use the term NSExtensionPointName, but use NSExtensionIdentifier to refer instead to the appex-specific identifier, such as com.apple.iCal.CalendarWidgetExtension. For the sake of clarity and consistency here, I’ll refer to the appex type identifier as NSExtensionPointName. Appex locations Many appexes supplied in macOS are stored as bundles inside dedicated collections such as /System/Library/ExtensionKit/Extensions or in frameworks. Where they are supplied in an app or similar bundle, they’re normally in a PlugIns folder, although according to this article QuickLook generators should be installed in Library/QuickLook, and Spotlight importers in Library/Spotlight. Types and management The rest of this article lists appex types, omitting the universal prefix com.apple., according to their management and discovery by PlugInKit during startup. I provide for each, as far as I’m able to tell, the type-specific manager, any controls provided in System Settings or elsewhere, and illustrative examples and other relevant information. Type-specific managers are those services or subsystems that PlugInKit hands over to during discovery. For example, when it discovers appexes that extend QuickLook by providing either thumbnails or previews, PlugInKit hands those over to com.apple.quicklook.ThumbnailsAgent to manage. Many appex types aren’t exposed in System Settings, are managed by PlugInKit, but don’t appear to undergo startup discovery. I have relegated those to the appendix at the end. Most of those are single-appex types, and others are only used by macOS. Appex types that are managed in System Settings and by PlugInKit, and undergo startup discovery: FinderSync, managed by the Finder, and controlled in File Providers settings, e.g. Keka Finder Integration quicklook.preview, managed by com.apple.quicklook.ThumbnailsAgent, and controlled in Quick Look settings; these are modern substitutes for qlgenerators quicklook.thumbnail, managed by com.apple.quicklook.ThumbnailsAgent, and controlled in Quick Look settings; these are modern substitutes for qlgenerators ui-services, managed by the Finder, and controlled in Actions settings, includes Markup, ShareSheetUI (not exposed in settings) Appex types that aren’t managed in System Settings, but are managed by PlugInKit, and undergo startup discovery: AppSSO.idp-extension, managed by AppSSOAgent, includes Kerberos and Sign In With Apple; these are single-sign-on extensions appstored-services.testflight, managed by appstoreagent; these handle App Store TestFlight AudioUnit, managed by AudioComponentRegistrar and axassetsd, for WardaSynthesizer AudioUnit-Speech, managed by AudioComponentRegistrar and axassetsd, include KonaSynthesizer and AUSPs AudioUnit-UI, managed by AudioComponentRegistrar cache_delete_extension, managed by deleted; these support app-specific cache management contacts.donation, managed by contactsdonationagent; these exchange info with Contacts ctk-tokens, managed by ctkd, include CryptoTokenKit and PlatformSSOToken; these handle tokens for CryptoTokenKit diagnosticextensions-service, managed by ControlCenter and diagnosticextensionsd, includes many service-specific Diagnostic Extensions email.extension, managed by maild, e.g. SpamSieve; these are Mail plugins fileprovider-nonui, managed by the Finder, includes iCloud Drive and PhotosFileProvider services, managed by the Finder; none listed spotlight.import, managed by mdbulkimport, includes PDFImporter spotlight.index, managed by corespotlightd, includes system extensions but not mdimporters textinputmethod-services, managed by imklaunchagent, includes many Input Methods usernotifications.content-extension, managed by NotificationCenter, includes ContentExtensions widgetkit-extension, managed by chronod, includes system and third-party widgets. Significant appex types that are managed by PlugInKit, but don’t undergo startup discovery: appintents-extension, multiple instances intents-service, many IntentsExtensions photo-editing, Photos editing, controlled in Photos Editing settings Safari.extension, Safari extensions, managed in Safari settings share-services, many Share extensions, managed in Sharing settings widget-extension, only a couple, e.g. iStat Menus. Appex types that apparently aren’t managed by PlugInKit, but are controlled in System Settings: Dock Tiles Finder, these are services offered in the Finder’s Services menu Spotlight, these are mdimporters. also Safari.content-blocker, which is managed in Safari settings rather than System Settings. Appex types that aren’t apparently managed by PlugInKit or controlled in System Settings: authentication-services-account-authentication-modification-ui authentication-services-credential-provider-ui broadcast-services-setupui broadcast-services-upload callkit.call-directory classkit.context-provider dt.Xcode.extension.source-editor fileprovider-actionsui identitylookup.classification-ui identitylookup.message-filter intents-ui-service keyboard-service networkextension.app-proxy photo-project tv-top-shelf Appendix: Appex types that aren’t exposed in System Settings, are managed by PlugInKit, but don’t undergo startup discovery System, multiple appexes: followup-extension – multiple FollowUpExtensions lighthouse.SAOrchestratedExtension – multiple Ingestors message-payload-provider – multiple mlhost.worker – many ML-related mlruntime.extension-point-high mlruntime.extension-point-ondemand mlruntime.extension-point-restricted screensaver – several ScreenSavers Settings.extension.ui – System Settings storagemanagement – many apps usernotifications.service – several NotificationServiceExtensions wallpaper – several Wallpapers System, single-app extensions: amsengagementd-extension – Books, News amsutility-extension – News app.non-ui-extension – Swift Playground app.non-ui-extension.multiple-instances – Swift Playground app.ui-extension.multiple-instances – Swift Playground applemediaservices.extensions.compose-review – ComposeReviewExtension askpermission-extension – App Store related askto.extension – AskToMessagesHost calendar.EventKitUIRemoteUIService – EventKitUIRemoteUIExtension calendar.virtualconference – FaceTimeExtension contact-view – System Service contacts.avatar-picker-ui – AvatarPickers deviceactivity.monitor-extension – ScreenTimeDeviceActivityMonitorExtension deviceactivityui.report-service – DeviceActivityReportService extension-view-service-sample-rk – RPVideoEditorExtension_macOS, ReplayKit extensionkit.app-extension-management – AppExtensionManagement extensionkit.app-extension-settings – ExtensionKit components facetime.notification – FaceTimeNotificationExtension feedback.drafting-extension – Feedback freeform.USD-renderer-remote-UI – USDRendererExtension fskit.fsmodule – exfat and msdos file systems (File System Extensions) GenerativePlaygroundUI.remoteUI – Image Playground groupactivities – FaceTime RemotePeoplePicker Home.ui-extension.userList – HomeUIUserList ImagePlayground.NonUIExtension – GPNonUIExtension ManagedSettings.service – ManagedClientMSExtension mapkit.private.RemoteUI – MKRemoteUI for MapKit mobileslideshow.photo-picker – PhotoPicker and PhotosPicker networkextension.packet-tunnel – network extensions PaperKit.extension.ui – PaperKitExtension PassKit.in-app-payment-ui – Wallet pdfkit-private – PDFExtensionView in PDFKit people-picker – System Service people.legacy.extension – PeopleLegacyMessageService Photos.MacMusicPickerExtension – PhotosMacMusicPickerExtension preference.security.privacy – Apple Advertising preference.sharing.service – Media Sharing private.translation-api-support – TranslationAPISupportExtension private.translation-ui – Translate private.voiceshortcuts-ui – three extensions replaykit.broadcast-picker – RPBroadcastActivityExtension_macOS in ReplayKit screentime.web-service – ScreenTimeWebExtension.