# clusteringIdentifier An identifier that determines whether the annotation view participates in clustering. ``` var clusteringIdentifier: String? { get set } ``` ## Discussion The default value of this property is `nil`, which prevents MapKit from clustering the annotation view with other annotation views. Setting the property to a non-`nil` value enables it to participate in clustering. Clustering occurs when there’s a collision between multiple annotation views with the same identifier on the map surface. MapKit removes the annotation views involved in the collision from the map view and replaces them with a clustering annotation view, which displays the title from one of the annotations and provides access to the other annotations. --- 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)