# Handling input from Apple Pencil Learn how to detect and respond to touches from Apple Pencil. ## Discussion UIKit reports touches from Apple Pencil in the same way it reports touches from a person’s fingers. Specifically, UIKit delivers a [`UITouch`](/documentation/UIKit/UITouch) object containing the location of the touch in your app. However, a touch object originating from Apple Pencil contains additional information, including the azimuth and altitude of Apple Pencil and the amount of force recorded at its tip.  Because Apple Pencil is a separate device, there’s a delay between the time Apple Pencil gathers altitude, azimuth, and force values and the time that those values are reported to your app. As a result, UIKit may provide *estimated* values for those properties initially, and then provide the real values at a later time. If you use altitude, azimuth, or force information from Apple Pencil, you must explicitly handle estimated properties. > Note: > Devices that work with Apple Pencil can report touches at up to 240 Hz. Because UIKit usually reports touches at around 60 Hz, any additional touches are coalesced into a single touch representing the last location. For information about how to get the additional touch data, see . ### Handle estimated properties When UIKit has only an estimate of a property’s value, it includes a flag in the [`estimatedPropertiesExpectingUpdates`](/documentation/UIKit/UITouch/estimatedPropertiesExpectingUpdates) property of the corresponding [`UITouch`](/documentation/UIKit/UITouch) object. When handling a touch event, check that property to determine if you need to update the touch information later. When a touch object contains estimated properties, UIKit also provides a value in the [`estimationUpdateIndex`](/documentation/UIKit/UITouch/estimationUpdateIndex) property. Use this value as a key to a dictionary that you maintain to identify the touch later. Set the value of that key to the app-specific object that you use to store the touch information. When UIKit later reports the real values, use the index to look up your app-specific object and replace the estimated values with the real values. The following code shows the `addSamples` method of an app that captures touch data. For each touch, the method creates a custom `StrokeSample` object with the touch information. If the force value of the touch is only an estimate, the `registerForEstimates` method caches the sample in a dictionary using the value in the [`estimationUpdateIndex`](/documentation/UIKit/UITouch/estimationUpdateIndex) property as the key. ```swift var estimates: [NSNumber: StrokeSample] func addSamples(for touches: [UITouch]) { if let stroke = strokeCollection?.activeStroke { for touch in touches { if touch == touches.last { let sample = StrokeSample(point: touch.location(in: self), forceValue: touch.force) stroke.add(sample: sample) registerForEstimates(touch: touch, sample: sample) } else { let sample = StrokeSample(point: touch.location(in: self), forceValue: touch.force, coalesced: true) stroke.add(sample: sample) registerForEstimates(touch: touch, sample: sample) } } self.setNeedsDisplay() } } func registerForEstimates(touch : UITouch, sample : StrokeSample) { if touch.estimatedPropertiesExpectingUpdates.contains(.force) { estimates[touch.estimationUpdateIndex!] = sample } } ``` When UIKit receives the actual values for a touch, it calls the [`touchesEstimatedPropertiesUpdated(_:)`](/documentation/UIKit/UIResponder/touchesEstimatedPropertiesUpdated(_:)) method of your responder or gesture recognizer. Use that method to replace estimated data with the real values provided by UIKit. The following code shows an example of the [`touchesEstimatedPropertiesUpdated(_:)`](/documentation/UIKit/UIResponder/touchesEstimatedPropertiesUpdated(_:)) method, which updates the force value for the cached `StrokeSample` objects created in the previous code example. The method uses the value in the [`estimationUpdateIndex`](/documentation/UIKit/UITouch/estimationUpdateIndex) property to retrieve the `StrokeSample` object from the `estimates` dictionary. It then updates the force value and removes the sample from the dictionary. ```swift override func touchesEstimatedPropertiesUpdated(_ touches: Set) { for touch in touches { // If the force value is no longer an estimate, update it. if !touch.estimatedPropertiesExpectingUpdates.contains(.force) { let index = touch.estimationUpdateIndex! var sample = estimates[index] sample?.force = touch.force // Remove the key and value from the dictionary. estimates.removeValue(forKey: index) } } } ``` ## Topics ### Related articles [Computing the perpendicular force of Apple Pencil](/documentation/UIKit/computing-the-perpendicular-force-of-apple-pencil) Adjust the force values reported by Apple Pencil so that they’re consistent with 3D Touch force values. --- 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)