# tapCreate(tap:place:options:eventsOfInterest:callback:userInfo:) Creates an event tap. ``` class func tapCreate(tap: CGEventTapLocation, place: CGEventTapPlacement, options: CGEventTapOptions, eventsOfInterest: CGEventMask, callback: CGEventTapCallBack, userInfo: UnsafeMutableRawPointer?) -> CFMachPort? ``` ## Parameters `tap` The location of the new event tap. Pass one of the constants listed in [`CGEventTapLocation`](/documentation/CoreGraphics/CGEventTapLocation). Only processes running as the root user may locate an event tap at the point where HID events enter the window server; for other users, this function returns `NULL`. `place` The placement of the new event tap in the list of active event taps. Pass one of the constants listed in [`CGEventTapPlacement`](/documentation/CoreGraphics/CGEventTapPlacement). `options` A constant that specifies whether the new event tap is a passive listener or an active filter. `eventsOfInterest` A bit mask that specifies the set of events to be observed. For a list of possible events, see [`CGEventType`](/documentation/CoreGraphics/CGEventType). For information on how to specify the mask, see [`CGEventMask`](/documentation/CoreGraphics/CGEventMask). If the event tap is not permitted to monitor one or more of the events specified in the `eventsOfInterest` parameter, then the appropriate bits in the mask are cleared. If that action results in an empty mask, this function returns `NULL`. `callback` An event tap callback function that you provide. Your callback function is invoked from the run loop to which the event tap is added as a source. The thread safety of the callback is defined by the run loop’s environment. To learn more about event tap callbacks, see [`CGEventTapCallBack`](/documentation/CoreGraphics/CGEventTapCallBack). `userInfo` A pointer to user-defined data. This pointer is passed into the callback function specified in the `callback` parameter. ## Return Value A Core Foundation mach port that represents the new event tap, or `NULL` if the event tap could not be created. When you are finished using the event tap, you should release the mach port using the function `CFRelease`. Releasing the mach port also releases the tap. ## Discussion Event taps receive key up and key down events if one of the following conditions is true: - The current process is running as the root user. - Access for assistive devices is enabled. In OS X v10.4, you can enable this feature using System Preferences, Universal Access panel, Keyboard view. After creating an event tap, you can add it to a run loop as follows: 1. Pass the event tap to the function to create a run loop event source. 2. Call the function to add the source to the appropriate run loop. --- 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)