# trackingImages A set of images that ARKit searches for and tracks in the user’s environment. ``` var trackingImages: Set { get set } ``` ## Discussion Add members to this set for each image that ARKit searches for in the user’s environment. When ARKit observes a matching image, the framework creates an [`ARImageAnchor`](/documentation/ARKit/ARImageAnchor) object and adds it to the session. If you set [`maximumNumberOfTrackedImages`](/documentation/ARKit/ARWorldTrackingConfiguration/maximumNumberOfTrackedImages) to a value greater than `1`, ARKit tracks multiple images as the session progresses, up to a maximum of four. To define the reference images that this property contains, create an asset catalog in Xcode or create [`ARReferenceImage`](/documentation/ARKit/ARReferenceImage) objects programmatically. For an example, see [Tracking and altering images](/documentation/ARKit/tracking-and-altering-images). --- 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)