# WebKit Constants WebKit constants affecting multiple classes. ## Topics ### WKPreview Constants [`let WKPreviewActionItemIdentifierAddToReadingList: String`](/documentation/WebKit/WKPreviewActionItemIdentifierAddToReadingList) Adds the item to the Reading List. [`let WKPreviewActionItemIdentifierCopy: String`](/documentation/WebKit/WKPreviewActionItemIdentifierCopy) Copies the item to the clipboard. [`let WKPreviewActionItemIdentifierOpen: String`](/documentation/WebKit/WKPreviewActionItemIdentifierOpen) Opens the item. [`let WKPreviewActionItemIdentifierShare: String`](/documentation/WebKit/WKPreviewActionItemIdentifierShare) Displays the Share panel options available for the item. ### WKWebsiteDataType Constants [`let WKWebsiteDataTypeCookies: String`](/documentation/WebKit/WKWebsiteDataTypeCookies) Cookies. [`let WKWebsiteDataTypeDiskCache: String`](/documentation/WebKit/WKWebsiteDataTypeDiskCache) On-disk caches. [`let WKWebsiteDataTypeIndexedDBDatabases: String`](/documentation/WebKit/WKWebsiteDataTypeIndexedDBDatabases) IndexedDB databases. [`let WKWebsiteDataTypeLocalStorage: String`](/documentation/WebKit/WKWebsiteDataTypeLocalStorage) HTML local storage. [`let WKWebsiteDataTypeMemoryCache: String`](/documentation/WebKit/WKWebsiteDataTypeMemoryCache) In-memory caches. [`let WKWebsiteDataTypeOfflineWebApplicationCache: String`](/documentation/WebKit/WKWebsiteDataTypeOfflineWebApplicationCache) HTML offline web app caches. [`let WKWebsiteDataTypeSessionStorage: String`](/documentation/WebKit/WKWebsiteDataTypeSessionStorage) HTML session storage. [`let WKWebsiteDataTypeWebSQLDatabases: String`](/documentation/WebKit/WKWebsiteDataTypeWebSQLDatabases) WebSQL databases. ### DOM Constants [`let DOMEventException: String`](/documentation/WebKit/DOMEventException) [`let DOMException: String`](/documentation/WebKit/DOMException) [`let DOMRangeException: String`](/documentation/WebKit/DOMRangeException) [`let DOMXPathException: String`](/documentation/WebKit/DOMXPathException) [`var DOM_BAD_BOUNDARYPOINTS_ERR: DOMRangeExceptionCode`](/documentation/WebKit/DOM_BAD_BOUNDARYPOINTS_ERR) [`var DOM_DOMSTRING_SIZE_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_DOMSTRING_SIZE_ERR) [`var DOM_HIERARCHY_REQUEST_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_HIERARCHY_REQUEST_ERR) [`var DOM_INDEX_SIZE_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_INDEX_SIZE_ERR) [`var DOM_INUSE_ATTRIBUTE_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_INUSE_ATTRIBUTE_ERR) [`var DOM_INVALID_ACCESS_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_INVALID_ACCESS_ERR) [`var DOM_INVALID_CHARACTER_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_INVALID_CHARACTER_ERR) [`var DOM_INVALID_EXPRESSION_ERR: DOMXPathExceptionCode`](/documentation/WebKit/DOM_INVALID_EXPRESSION_ERR) [`var DOM_INVALID_MODIFICATION_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_INVALID_MODIFICATION_ERR) [`var DOM_INVALID_NODE_TYPE_ERR: DOMRangeExceptionCode`](/documentation/WebKit/DOM_INVALID_NODE_TYPE_ERR) [`var DOM_INVALID_STATE_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_INVALID_STATE_ERR) [`var DOM_NAMESPACE_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_NAMESPACE_ERR) [`var DOM_NOT_FOUND_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_NOT_FOUND_ERR) [`var DOM_NOT_SUPPORTED_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_NOT_SUPPORTED_ERR) [`var DOM_NO_DATA_ALLOWED_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_NO_DATA_ALLOWED_ERR) [`var DOM_NO_MODIFICATION_ALLOWED_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_NO_MODIFICATION_ALLOWED_ERR) [`var DOM_SYNTAX_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_SYNTAX_ERR) [`var DOM_TYPE_ERR: DOMXPathExceptionCode`](/documentation/WebKit/DOM_TYPE_ERR) [`var DOM_UNSPECIFIED_EVENT_TYPE_ERR: DOMEventExceptionCode`](/documentation/WebKit/DOM_UNSPECIFIED_EVENT_TYPE_ERR) [`var DOM_WRONG_DOCUMENT_ERR: DOMExceptionCode`](/documentation/WebKit/DOM_WRONG_DOCUMENT_ERR) ### WebKit Constants (Legacy) [`let WebActionButtonKey: String`](/documentation/WebKit/WebActionButtonKey) An NSNumber object where `0` indicates the left button, `1` indicates the middle button, and `2` indicates the right button. [`let WebActionElementKey: String`](/documentation/WebKit/WebActionElementKey) A dictionary containing element information. See [`WebView`](/documentation/WebKit/WebView-swift.class) for a description of the key-value pairs in this dictionary. [`let WebActionModifierFlagsKey: String`](/documentation/WebKit/WebActionModifierFlagsKey) An unsigned number that indicates the modifier flag. [`let WebActionNavigationTypeKey: String`](/documentation/WebKit/WebActionNavigationTypeKey) The navigation type of the action. Can be any of the values defined in [`WebNavigationType`](/documentation/WebKit/WebNavigationType) below. [`let WebActionOriginalURLKey: String`](/documentation/WebKit/WebActionOriginalURLKey) The URL that initiated the action. [`let WebArchivePboardType: String`](/documentation/WebKit/WebArchivePboardType) The pasteboard type constant used when adding or accessing a WebArchive on the pasteboard. [`let WebElementDOMNodeKey: String`](/documentation/WebKit/WebElementDOMNodeKey) The DOMNode for this element. [`let WebElementFrameKey: String`](/documentation/WebKit/WebElementFrameKey) The WebFrame object associated with this element. [`let WebElementImageAltStringKey: String`](/documentation/WebKit/WebElementImageAltStringKey) An NSString of the ALT attribute of an image element. [`let WebElementImageKey: String`](/documentation/WebKit/WebElementImageKey) An NSImage representing an image element. [`let WebElementImageRectKey: String`](/documentation/WebKit/WebElementImageRectKey) An NSValue containing an NSRect, the size of an image element. [`let WebElementImageURLKey: String`](/documentation/WebKit/WebElementImageURLKey) An NSURL containing the location of an image element. [`let WebElementIsSelectedKey: String`](/documentation/WebKit/WebElementIsSelectedKey) An NSNumber used as a BOOL value to indicate whether a text element is selected or not. Zero value indicates false, true otherwise. [`let WebElementLinkLabelKey: String`](/documentation/WebKit/WebElementLinkLabelKey) An NSString containing the text within an anchor. [`let WebElementLinkTargetFrameKey: String`](/documentation/WebKit/WebElementLinkTargetFrameKey) The WebFrame object associated with the target of the anchor. [`let WebElementLinkTitleKey: String`](/documentation/WebKit/WebElementLinkTitleKey) An NSString containing the title of an anchor. [`let WebElementLinkURLKey: String`](/documentation/WebKit/WebElementLinkURLKey) An NSURL containing the location of a link if the element is within an anchor. [`let WebHistoryItemsKey: String`](/documentation/WebKit/WebHistoryItemsKey) The key to access an array containing the added or removed web history items. [`let WebKitErrorDomain: String`](/documentation/WebKit/WebKitErrorDomain) [`let WebKitErrorMIMETypeKey: String`](/documentation/WebKit/WebKitErrorMIMETypeKey) [`let WebKitErrorPlugInNameKey: String`](/documentation/WebKit/WebKitErrorPlugInNameKey) [`let WebKitErrorPlugInPageURLStringKey: String`](/documentation/WebKit/WebKitErrorPlugInPageURLStringKey) [`let WebPlugInAttributesKey: String`](/documentation/WebKit/WebPlugInAttributesKey) The `NSDictionary` object containing all names and values of all attributes of the plug-in’s associated HTML element, as well as all names and values of the parameters to be passed to the plug-in. For example, this dictionary will contain all `PARAM` elements within an `APPLET` element. If attribute and parameter names conflict, the attributes of an element take precedence over any of its parameters. All keys and values in this dictionary must be of type `NSString`. *Required key*. [`let WebPlugInBaseURLKey: String`](/documentation/WebKit/WebPlugInBaseURLKey) The base URL of the document containing the plug-in’s view. *Required key*. [`let WebPlugInContainerKey: String`](/documentation/WebKit/WebPlugInContainerKey) An object that conforms to the `WebPlugInContainer` informal protocol. This object is used for callbacks from the plug-in to the enclosing application. If `WebPlugInContainerKey` is `nil`, no callbacks will occur. [`let WebPlugInContainingElementKey: String`](/documentation/WebKit/WebPlugInContainingElementKey) If an element of the page’s Document Object Model was used to specify the plug-in, this will contain that element. Otherwise, it will be `nil`. [`let WebPlugInShouldLoadMainResourceKey: String`](/documentation/WebKit/WebPlugInShouldLoadMainResourceKey) A Boolean value indicating whether the plug-in should load its own main resource (the `src` URL, in most cases). ### WebKit Constants (Legacy) [`let WebActionButtonKey: String`](/documentation/WebKit/WebActionButtonKey) An NSNumber object where `0` indicates the left button, `1` indicates the middle button, and `2` indicates the right button. [`let WebActionElementKey: String`](/documentation/WebKit/WebActionElementKey) A dictionary containing element information. See [`WebView`](/documentation/WebKit/WebView-swift.class) for a description of the key-value pairs in this dictionary. [`let WebActionModifierFlagsKey: String`](/documentation/WebKit/WebActionModifierFlagsKey) An unsigned number that indicates the modifier flag. [`let WebActionNavigationTypeKey: String`](/documentation/WebKit/WebActionNavigationTypeKey) The navigation type of the action. Can be any of the values defined in [`WebNavigationType`](/documentation/WebKit/WebNavigationType) below. [`let WebActionOriginalURLKey: String`](/documentation/WebKit/WebActionOriginalURLKey) The URL that initiated the action. [`let WebArchivePboardType: String`](/documentation/WebKit/WebArchivePboardType) The pasteboard type constant used when adding or accessing a WebArchive on the pasteboard. [`let WebElementDOMNodeKey: String`](/documentation/WebKit/WebElementDOMNodeKey) The DOMNode for this element. [`let WebElementFrameKey: String`](/documentation/WebKit/WebElementFrameKey) The WebFrame object associated with this element. [`let WebElementImageAltStringKey: String`](/documentation/WebKit/WebElementImageAltStringKey) An NSString of the ALT attribute of an image element. [`let WebElementImageKey: String`](/documentation/WebKit/WebElementImageKey) An NSImage representing an image element. [`let WebElementImageRectKey: String`](/documentation/WebKit/WebElementImageRectKey) An NSValue containing an NSRect, the size of an image element. [`let WebElementImageURLKey: String`](/documentation/WebKit/WebElementImageURLKey) An NSURL containing the location of an image element. [`let WebElementIsSelectedKey: String`](/documentation/WebKit/WebElementIsSelectedKey) An NSNumber used as a BOOL value to indicate whether a text element is selected or not. Zero value indicates false, true otherwise. [`let WebElementLinkLabelKey: String`](/documentation/WebKit/WebElementLinkLabelKey) An NSString containing the text within an anchor. [`let WebElementLinkTargetFrameKey: String`](/documentation/WebKit/WebElementLinkTargetFrameKey) The WebFrame object associated with the target of the anchor. [`let WebElementLinkTitleKey: String`](/documentation/WebKit/WebElementLinkTitleKey) An NSString containing the title of an anchor. [`let WebElementLinkURLKey: String`](/documentation/WebKit/WebElementLinkURLKey) An NSURL containing the location of a link if the element is within an anchor. [`extern NSString * WebHistoryAllItemsRemovedNotification;`](/documentation/WebKit/WebHistoryAllItemsRemovedNotification) Posted when all history items have been removed from the web history. [`extern NSString * WebHistoryItemChangedNotification;`](/documentation/WebKit/WebHistoryItemChangedNotification) Posted by a WebHistoryItem object when the value of the history item’s title, alternate title, URL strings, or last visited interval changes. [`extern NSString * WebHistoryItemsAddedNotification;`](/documentation/WebKit/WebHistoryItemsAddedNotification) Posted when history items have been added to a web history. [`let WebHistoryItemsKey: String`](/documentation/WebKit/WebHistoryItemsKey) The key to access an array containing the added or removed web history items. [`extern NSString * WebHistoryItemsRemovedNotification;`](/documentation/WebKit/WebHistoryItemsRemovedNotification) Posted when items have been removed from the web history. [`extern NSString * WebHistoryLoadedNotification;`](/documentation/WebKit/WebHistoryLoadedNotification) Posted when web history items have been loaded from a URL. [`extern NSString * WebHistorySavedNotification;`](/documentation/WebKit/WebHistorySavedNotification) Posted when web history items have been saved to a URL. [`let WebKitErrorDomain: String`](/documentation/WebKit/WebKitErrorDomain) [`let WebKitErrorMIMETypeKey: String`](/documentation/WebKit/WebKitErrorMIMETypeKey) [`let WebKitErrorPlugInNameKey: String`](/documentation/WebKit/WebKitErrorPlugInNameKey) [`let WebKitErrorPlugInPageURLStringKey: String`](/documentation/WebKit/WebKitErrorPlugInPageURLStringKey) [`let WebPlugInAttributesKey: String`](/documentation/WebKit/WebPlugInAttributesKey) The `NSDictionary` object containing all names and values of all attributes of the plug-in’s associated HTML element, as well as all names and values of the parameters to be passed to the plug-in. For example, this dictionary will contain all `PARAM` elements within an `APPLET` element. If attribute and parameter names conflict, the attributes of an element take precedence over any of its parameters. All keys and values in this dictionary must be of type `NSString`. *Required key*. [`let WebPlugInBaseURLKey: String`](/documentation/WebKit/WebPlugInBaseURLKey) The base URL of the document containing the plug-in’s view. *Required key*. [`let WebPlugInContainerKey: String`](/documentation/WebKit/WebPlugInContainerKey) An object that conforms to the `WebPlugInContainer` informal protocol. This object is used for callbacks from the plug-in to the enclosing application. If `WebPlugInContainerKey` is `nil`, no callbacks will occur. [`let WebPlugInContainingElementKey: String`](/documentation/WebKit/WebPlugInContainingElementKey) If an element of the page’s Document Object Model was used to specify the plug-in, this will contain that element. Otherwise, it will be `nil`. [`let WebPlugInShouldLoadMainResourceKey: String`](/documentation/WebKit/WebPlugInShouldLoadMainResourceKey) A Boolean value indicating whether the plug-in should load its own main resource (the `src` URL, in most cases). [`extern NSString * WebPreferencesChangedNotification;`](/documentation/WebKit/WebPreferencesChangedNotification) Posted when the web preference settings are changed. [`extern NSString * const WebViewDidBeginEditingNotification;`](/documentation/WebKit/WebViewDidBeginEditingNotification) Posted when a web view begins any operation that changes its contents in response to user editing. [`extern NSString * const WebViewDidChangeNotification;`](/documentation/WebKit/WebViewDidChangeNotification) Posted when a web view performs any operation that changes its contents in response to user editing. [`extern NSString * const WebViewDidChangeSelectionNotification;`](/documentation/WebKit/WebViewDidChangeSelectionNotification) Posted when a web view changes its typing selection. [`extern NSString * const WebViewDidChangeTypingStyleNotification;`](/documentation/WebKit/WebViewDidChangeTypingStyleNotification) Posted when a web view changes its typing style. [`extern NSString * const WebViewDidEndEditingNotification;`](/documentation/WebKit/WebViewDidEndEditingNotification) Posted when a web view ends any operation that changes its contents in response to user editing. [`extern NSString * WebViewProgressEstimateChangedNotification;`](/documentation/WebKit/WebViewProgressEstimateChangedNotification) Posted by a WebView object when the estimated progress value of a load changes. [`extern NSString * WebViewProgressFinishedNotification;`](/documentation/WebKit/WebViewProgressFinishedNotification) Posted by a WebView object when the load has finished. [`extern NSString * WebViewProgressStartedNotification;`](/documentation/WebKit/WebViewProgressStartedNotification) Posted by a WebView object when a load begins, including a load that is initiated in a subframe. ### Constants [`let WKErrorDomain: String`](/documentation/WebKit/WKErrorDomain) String that identifies the WebKit error domain. [`let WKWebsiteDataTypeFetchCache: String`](/documentation/WebKit/WKWebsiteDataTypeFetchCache) [`let WKWebsiteDataTypeFileSystem: String`](/documentation/WebKit/WKWebsiteDataTypeFileSystem) [`let WKWebsiteDataTypeHashSalt: String`](/documentation/WebKit/WKWebsiteDataTypeHashSalt) [`let WKWebsiteDataTypeMediaKeys: String`](/documentation/WebKit/WKWebsiteDataTypeMediaKeys) [`let WKWebsiteDataTypeSearchFieldRecentSearches: String`](/documentation/WebKit/WKWebsiteDataTypeSearchFieldRecentSearches) [`let WKWebsiteDataTypeServiceWorkerRegistrations: String`](/documentation/WebKit/WKWebsiteDataTypeServiceWorkerRegistrations) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)