# Clustering annotations Combine multiple annotations into a single clustered annotation. ## Discussion Annotations display coordinate-specific data on a map, typically in the form of markers or images. To declutter annotation-heavy maps, MapKit JS supports *annotation clustering*. As the user zooms out on a map that contains annotations, MapKit JS groups individual annotations into a *cluster annotation* if they collide and if they share the same [`clusteringIdentifier`](/documentation/MapKitJS/Annotation/clusteringIdentifier). The cluster annotation’s [`memberAnnotations`](/documentation/MapKitJS/Annotation/memberAnnotations) property lists the individual annotations within the cluster. By default, a cluster annotation’s marker displays its member count. MapKit JS creates cluster annotations automatically. Although you can’t instantiate a cluster annotation, you can customize the look of cluster annotations by providing a delegate method, [`annotationForCluster`](/documentation/MapKitJS/Map/annotationForCluster), to the map. ### Understand the annotations arrays Although visible on a map, cluster annotations aren’t members of the map’s [`annotations`](/documentation/MapKitJS/Map/annotations) array. The annotations that make up the cluster do belong to the [`annotations`](/documentation/MapKitJS/Map/annotations) array, however, even if they’re not individually visible on the map. For example, the following figure shows a map with annotations A, B, C, D, and E:  If the user zooms out so A, B, and C overlap on the map, the annotations combine to create cluster annotation Q, as in the following figure:  The map displays annotations Q, D, and E, and the resulting annotation arrays are: - `Q.memberAnnotations = [A, B, C];` - `map.annotations = [A, B, C, D, E];` ### Set cluster annotation properties Cluster annotations have the same properties as other annotations, but you can’t set some values, including [`coordinate`](/documentation/MapKitJS/Annotation/coordinate), [`clusteringIdentifier`](/documentation/MapKitJS/Annotation/clusteringIdentifier), and [`draggable`](/documentation/MapKitJS/Annotation/draggable). Other values have specific defaults as the following table shows: |Property |Default for clustering |Description | |-----------------------------------------------------------------------------------|---------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| |``doc://com.apple.mapkitjs/documentation/MapKitJS/Annotation/title`` |The `title` of the member annotation with the highest priority.|The annotation title text. | |``doc://com.apple.mapkitjs/documentation/MapKitJS/Annotation/subtitle`` |“`+N` more”, where `N + 1` is the number of member annotations.|The annotation subtitle text. | |``doc://com.apple.mapkitjs/documentation/MapKitJS/Annotation/coordinate`` |The average of the member annotation coordinates. |The annotation’s coordinate. The system automatically sets the coordinate of a cluster annotation to the average of all of the contained member annotation coordinates. You can’t change this value; therefore, the user can’t ever drag a cluster annotation.| |``doc://com.apple.mapkitjs/documentation/MapKitJS/MarkerAnnotation/glyphText`` |`N + 1` (the number of member annotations). |The annotation glyph text. | |``doc://com.apple.mapkitjs/documentation/MapKitJS/Annotation/draggable`` |`false` |Determines whether the user may drag the annotation. You can’t modify this property. | |``doc://com.apple.mapkitjs/documentation/MapKitJS/Annotation/memberAnnotations`` |NA |A flat array containing all annotations within the cluster annotation. Only cluster annotations have a `memberAnnotations` property. You can’t modify this property. | |``doc://com.apple.mapkitjs/documentation/MapKitJS/Annotation/clusteringIdentifier``|`null` |A shared identifier for all of the member annotations. An annotation needs a `clusteringIdentifier` to be part of an annotation cluster. | ## Topics [`ClusterAnnotation`](/documentation/MapKitJS/ClusterAnnotation) An annotation type that groups multiple annotations together. --- 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)